JP2015195533A - communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel technique for a communication device to appropriately execute unicast communication with another communication device.SOLUTION: A printer PR receives a search packet from a terminal device TE (T14), and transmits a response packet to the terminal device TE (T16). The printer PR, when judging that the value of the network address part of an IPte does not match the value of the network address part of an IPpr (T20), newly sets an IPca1, as the IP address of the printer PR (T36). Then, the printer PR again receives a search packet again from the terminal device TE (T40), and transmits a response packet to the terminal device TE (T42). Thus, the printer PR can notify the terminal device TE of the IPca1 which is newly set to the printer PR. As a result, the printer PR executes unicast communication of print data using the IPca1 with the terminal device TE (T48).

Description

  The present specification discloses a communication apparatus for executing communication with another communication apparatus.

  In the technique disclosed in Patent Document 1, when a printer receives a name resolution packet broadcast from a PC to a local area network, the printer transmits a PING packet to the PC. If the printer does not receive a response packet to the PING packet from the PC, the printer determines that unicast communication with the printer cannot be performed, and sets a new IP address for the printer itself.

JP 2012-156910 A

  The present specification discloses a novel technique for a communication device to appropriately perform unicast communication with another communication device.

  The first communication device disclosed in the present specification includes a request packet receiving unit, a response packet transmitting unit, a determining unit, a setting unit, and a unicast communication executing unit. The request packet receiving unit receives a request packet broadcast to a local area network from a second communication device different from the first communication device. The request packet includes a target IP address that is the current IP address of the second communication device and a target subnet mask that is the current subnet mask of the second communication device. When a request packet is received from the second communication device, the response packet transmission unit transmits a first response packet for the request packet to the second communication device via the local area network. The first response packet includes a current IP address that is the current IP address of the first communication device and a current subnet mask that is the current subnet mask of the first communication device. The determination unit is the value of the network address part of the target IP address using the value of the target IP address and the value of the target subnet mask included in the request packet when the request packet is received from the second communication device. A target network address value is specified, a current network address value that is a value of the network address portion of the current IP address is specified using the current IP address value and the current subnet mask value, and the specified target network address value It is determined whether or not the specified current network address value matches. When it is determined that the target network address value does not match the current network address value, the setting unit replaces the current IP address with the network address that matches the target network address value as the IP address of the first communication device. Set a new IP address that contains the value of the part. The unicast communication execution unit performs unicast communication of target data using the new IP address via the local area network after the new IP address is set as the IP address of the first communication device. And execute. The request packet receiver further receives the request packet broadcast again from the second communication device to the local area network after the new IP address is set as the IP address of the first communication device. The response packet transmission unit further includes a second response packet that includes the new IP address and is a second response packet to the request packet via the local area network when the request packet is received again from the second communication device. The response packet is transmitted to the second communication device. After the second response packet is transmitted to the second communication device, the unicast communication execution unit performs unicast communication of the target data using the new IP address with the second communication device via the local area network. Run.

  According to the above configuration, the first communication device receives the request packet broadcast from the second communication device, transmits the first response packet to the second communication device, the target network address value and the current network It is determined whether or not the address value matches. When determining that the target network address value does not match the current network address value, the first communication device sets a new IP address instead of the current IP address as the IP address of the first communication device. The first communication device receives the request packet broadcast again from the second communication device, and receives the second response packet including the new IP address including the value of the network address portion that matches the target network address value. Is transmitted to the second communication device. That is, the first communication device can notify the second communication device of the new IP address. Thereby, the 1st communication apparatus can perform appropriately the unicast communication of the object data using a new IP address with the 2nd communication apparatus.

  The present specification further discloses a communication system including the first communication device and the second communication device. The second communication device includes a request packet transmission unit, a response packet reception unit, and a first determination unit. The request packet transmission unit broadcasts the request packet to the local area network to which the first communication device and the second communication device are connected. The request packet includes a target IP address that is the current IP address of the second communication device and a target subnet mask that is the current subnet mask of the second communication device. The response packet receiving unit receives a first response packet for the request packet from the first communication device via the local area network. The first response packet includes a current IP address that is the current IP address of the first communication device and a current subnet mask that is the current subnet mask of the first communication device. When the first response packet is received from the first communication device, the first determination unit uses the value of the target IP address and the value of the target subnet mask to determine the value of the network address part of the target IP address. Identify the target network address value, identify the current network address value that is the value of the network address part of the current IP address using the current IP address value and the current subnet mask value included in the response packet, and have already been identified It is determined whether or not the target network address value matches the specified current network address value. The request packet transmission unit further broadcasts the request packet to the local area network again when the first determination unit determines that the target network address value does not match the current network address value. The response packet receiving unit further sets the first IP address of the first communication device after the new IP address including the value of the network address part matching the target network address value is set instead of the current IP address. The second response packet including the new IP address, which is a second response packet to the request packet broadcast again via the local area network, is received from the communication device.

  According to the above configuration, since the first communication device notifies the second communication device of the new IP address, the second communication device can know the new IP address of the first communication device. Thereby, the 1st communication apparatus and the 2nd communication apparatus can perform appropriately the unicast communication of the object data using a new IP address.

  The single unit of the second communication device is also new and useful. A control method for realizing at least one of the first and second communication devices, a computer program, and a computer-readable recording medium storing the computer program are also novel and useful.

1 shows a configuration of a communication system. 2 shows a flowchart of processing of the printer of the first embodiment. The selection screen displayed on the display part of a printer is shown. The flowchart of the process of the terminal device of 1st Example is shown. The sequence diagram of case A in which change of the IP address is selected is shown. The sequence diagram of case B in which change of the IP address is not selected is shown. 6 shows a flowchart of processing of a printer of a second embodiment. The sequence diagram of 2nd Example is shown. 9 shows a flowchart of processing of a printer of a third embodiment. The sequence diagram of 3rd Example is shown.

(First embodiment)
(Configuration of communication system 2; FIG. 1)
As shown in FIG. 1, the communication system 2 includes a terminal device TE, a printer PR, a first DHCP (abbreviation of Dynamic Host Configuration Protocol) server 60, and a second DHCP server 70. The devices TE, PR, 60 and 70 are connected to the LAN 4 and can communicate with each other via the LAN 4. The LAN 4 is a wired LAN in the present embodiment, but may be a wireless LAN in a modified example.

(Configuration of printer PR)
The printer PR is a peripheral device that can execute a printing function (that is, a peripheral device such as the terminal device TE). The printer PR includes an operation unit 12, a display unit 14, a print execution unit 16, a network interface 18, and a control unit 20.

  The operation unit 12 includes a plurality of keys. The user can input various instructions to the printer PR by operating the operation unit 12. The display unit 14 is a display for displaying various information. The printing execution unit 16 includes a printing mechanism such as an inkjet head method or a laser method, and executes printing in accordance with an instruction from the control unit 20. The network interface 18 is connected to the LAN 4. Hereinafter, the interface is described as “I / F”.

  The control unit 20 includes a CPU 22 and a memory 24. The CPU 22 is a processor that executes various processes in accordance with a program (for example, a specific program described later) stored in the memory 24. Further, the memory 24 stores the current IP address value IPpr of the printer PR and the current subnet mask value SMpr of the printer PR. The value IPpr and the value SMpr are “192.168.100.2” and “255.255.255.0”, respectively. In the state of FIG. 1, these values IPpr and SMpr are assigned by the second DHCP server 70 connected to the LAN 4. In the following, the value IPpr and the value SMpr may be abbreviated as “IPpr” and “SMpr”, respectively. The specific program stored in the memory 24 will be described later.

(Terminal device TE)
The terminal device TE is a stationary terminal device such as a desktop PC. In a modification, the terminal device TE may be a portable terminal device such as a notebook PC or a tablet PC. The terminal device TE includes a control unit 50. The control unit 50 includes a CPU 52 and a memory 54. The CPU 52 is a processor that executes various processes in accordance with programs (for example, OS programs, specific programs, etc.) stored in the memory 54. Further, the memory 54 stores the current IP address value IPte of the terminal device TE and the current subnet mask value SMte of the terminal device TE. The value IPte and the value SMte are “192.168.1.2” and “255.255.255.0”, respectively. That is, the value of the network address part of the IP address of the terminal device TE is “192.168.1”. In the state of FIG. 1, these values IPte and SMte are assigned by the first DHCP server 60 connected to the LAN 4. In the following, the values IPte and SMte may be abbreviated as “IPte” and “SMte”, respectively.

  The memory 54 stores the specific program and the printer driver. The printer driver is a program for causing the printer PR to execute a printing function. As described above, the specific program is provided in each of the terminal device TE and the printer PR. When the terminal device TE and the printer PR belong to different subnets, the specific program is lower than the application layer of the OSI reference model (for example, the physical layer, the data link layer, etc.) between the terminal device TE and the printer PR. It is a program for executing unicast communication of data. Here, “the terminal device TE and the printer PR belong to different subnets” means that the value of the network address part (for example, 192.168.1. 1) of the IP address of the terminal device TE and the network address of the IP address of the printer PR. This means that the value of the part (for example, 192.168.100) is different.

  When the terminal device TE and the printer PR belong to different subnets, normally, unicast communication cannot be performed between the terminal device TE and the printer PR. For example, when the terminal device TE transmits data using the IP address of the printer PR as the transmission destination IP address, the data is transmitted to the gateway of the terminal device TE. In the present embodiment, the first DHCP server 60 realizes the function of the gateway. In the state of FIG. 1, the value of the network address part of the IP address of the first DHCP server 60 (ie, gateway) (ie, 192.168.1) matches the value of the network address part of the IP address of the terminal device TE. However, it does not match the value of the network address part (namely, 192.168.100) of the IP address of the printer PR that is the data transmission destination. Therefore, even if the first DHCP server 60 receives the data from the terminal device TE, the first DHCP server 60 does not transmit the data to the printer PR. As a result, the terminal device TE cannot execute unicast communication with the printer PR.

  On the other hand, since the printer PR and the terminal device TE according to the present embodiment include the specific program, the unicast communication is directly performed according to the specific program without passing through the gateway of the terminal device TE (that is, the first DHCP server 60). Can be executed automatically.

  The specific program and the printer driver are stored in, for example, an information storage medium (CD, DVD, etc.) packaged with the printer PR when the printer PR is shipped. The terminal device TE installs these programs stored in the information storage medium, and stores these programs in the memory 54. Further, when the terminal device TE installs a printer driver and generates a print port for the printer PR, the terminal device TE acquires the node name of the printer PR from the printer PR. The terminal device TE stores the node name of the printer PR in the memory 54.

(Configuration of the first DHCP server 60)
The first DHCP server 60 assigns an IP address and a subnet mask to the above device in response to a request from a device (for example, terminal device TE, printer PR, etc.) connected to the LAN 4. The first DHCP server 60 has a gateway function for receiving data from one device and transferring the received data to another device. The range of IP addresses that can be assigned by the first DHCP server 60 (ie, “192.168.1.2 to 254”) is determined in advance. The first DHCP server 60 uses the value IPdh1 “192.168.1.1” as its own IP address (ie, gateway address) and the value SMdh1 “255.255.255.0” as its own subnet mask. Use as Hereinafter, the value IPdh1 and the value SMdh1 may be abbreviated as “IPdh1” and “SMdh1”, respectively.

(Configuration of the second DHCP server 70)
The second DHCP server 70 is a DHCP server different from the first DHCP server 60, and assigns an IP address and a subnet mask to the above device in response to a request from a device connected to the LAN 4. The second DHCP server 70 has a gateway function. The second DHCP server 60 can assign an IP address in the range of “192.168.100.2 to 254”. The second DHCP server 70 uses the value IPdh2 “192.168.100.1” as its own IP address (ie, gateway address) and uses the value SMdh2 “255.255.255.0” as its own subnet mask. Use as Hereinafter, the value IPdh2 and the value SMdh2 may be abbreviated as “IPdh2” and “SMdh2”, respectively.

  In this embodiment, two DHCP servers 60 and 70 are connected to the LAN 4. In such a situation, in the state of FIG. 1, IPte is assigned to the terminal device TE by the first DHCP server 60, and the IPpr is assigned to the printer PR by the second DHCP server 70 different from the first DHCP server 60. Can be assigned. In such a situation, the value of the network address part of IPte (that is, 192.168.1) does not match the value of the network address part of IPpr (that is, 192.168.100). For this reason, it is impossible to execute unicast communication via the gateway between the printer PR and the terminal device TE. If such a situation continues, the printer PR cannot properly receive the print data, and the printer PR cannot execute printing. In order to suppress the occurrence of such an event, in the present embodiment, the printer PR and the terminal device TE execute the process of FIG. 2 and the process of FIG. 4, respectively.

(Processing executed by printer PR)
Next, the contents of processing executed by the CPU 22 of the printer PR will be described with reference to FIG. In S10, the CPU 22 monitors reception of the search packet. The search packet is a packet broadcast from the terminal apparatus TE to the LAN 4 and includes the node name of the printer PR, the IP address (for example, IPte) of the terminal apparatus TE, and the subnet mask (for example, SMte) of the terminal apparatus TE. . The search packet is broadcast from the terminal apparatus TE when the printing instruction is transmitted from the terminal apparatus TE to the printer PR but the printing is not executed by the printer PR (that is, when printing fails in the printer PR). The

  When receiving the search packet including the node name of the printer PR, the CPU 22 determines YES in S10 and proceeds to S12.

  In S12, the CPU 22 executes unicast communication according to the specific program and transmits a response packet to the search packet to the terminal device TE. Accordingly, even if the terminal device TE and the printer PR belong to different subnets, the printer PR can appropriately transmit a response packet to the search packet to the terminal device TE. The response packet includes the current IP address (for example, IPpr) of the printer PR and the current subnet mask (for example, SMpr) of the printer PR.

  In S14, the CPU 22 determines whether or not the value of the network address part of the IP address of the terminal device TE matches the value of the network address part of the IP address of the printer PR. Specifically, the CPU 22 uses the value of the IP address of the terminal device TE and the value of the subnet mask of the terminal device TE included in the search packet received in S10, and the network address portion of the IP address of the terminal device TE. Value (for example, “192.168.1”) is specified. Further, the CPU 22 uses the IP address value of the printer PR and the subnet mask value of the printer PR, which are stored in the memory 24, for example, the value of the network address portion of the IP address of the printer PR (for example, “192.168 .. 100 "). Then, the CPU 22 determines whether or not the two specified values match.

  If the CPU 22 determines that the value of the network address part of the IP address of the terminal device TE matches the value of the network part of the IP address of the printer PR (YES in S14), the process of FIG. . On the other hand, if the CPU 22 determines that the value of the network address part of the IP address of the terminal device TE does not match the value of the network part of the IP address of the printer PR (NO in S14), the process proceeds to S16. .

  In S16, the CPU 22 displays a selection screen on the display unit 14 of the printer PR. As shown in FIG. 3, the selection screen is a screen for allowing the user to select whether or not to change the value of the IP address of the printer PR.

  In S18, the CPU 22 determines whether or not the user has selected to change the value of the IP address of the printer PR. Specifically, when the user selects the YES button 110 indicating that the value of the IP address of the printer PR should be changed on the selection screen of FIG. 3, the CPU 22 determines YES in S18, and proceeds to S20. move on. On the other hand, when the user selects the NO button 112 indicating that the value of the IP address of the printer PR should not be changed on the selection screen of FIG. 3, the CPU 22 determines NO in S18 and proceeds to S19. .

  In S19, the CPU 22 executes unicast communication according to the specific program, and transmits a non-change notification indicating that the value of the IP address of the printer PR is not changed to the terminal device TE. When S19 ends, the process of FIG. 2 ends.

  In S <b> 20, the CPU 22 broadcasts DHCP Discover to the LAN 4. The DHCP Discover includes the MAC address of the printer PR that is the transmission source of the DHCP Discover.

  Each device (for example, the terminal device TE, the first and second DHCP servers 60 and 70) connected to the LAN 4 receives the DHCP Discover. Devices other than the DHCP server (for example, the terminal device TE) do not respond even if they receive the DHCP Discover.

  On the other hand, when the first DHCP server 60 receives the DHCP Discover, it broadcasts the DHCP Offer to the LAN 4. The DHCP Offer is a candidate IP address value IPca1 which is a candidate for an IP address to be newly set in the printer PR, a subnet mask value SMdh1 of the first DHCP server 60, and an IP address of the first DHCP server 60. Value IPdh1. The DHCP Offer further includes the MAC address of the printer PR included in the DHCP Discover. For this reason, even if a device other than the printer PR (for example, the terminal device TE) receives the DHCP Offer, it does not execute a process corresponding to the DHCP Offer.

  Similarly, when receiving the DHCP Discover, the second DHCP server 70 broadcasts the DHCP Offer to the LAN 4. The DHCP Offer includes a candidate IP address value IPca2, a subnet mask value SMdh2 of the second DHCP server 70, an IP address value IPdh2 of the second DHCP server 70, and a MAC address of the printer PR.

  In S <b> 22, the CPU 22 receives one DHCP Offer from each of the first DHCP server 60 and the second DHCP server 70.

  Next, in S24, the CPU 22 selects one candidate IP address from two candidate IP addresses included in the two received DHCP Offers. Specifically, first, the CPU 22 uses the IP address value (for example, IPte) of the terminal device TE and the subnet mask (for example, SMte) of the terminal device TE included in the search packet received in S10 of FIG. The value of the network address part of the IP address of the terminal device TE is specified. Next, the CPU 22 specifies the value of the network address portion of IPca1 using IPca1 and SMdh1 included in the DHCP Offer received from the first DHCP server 60. Similarly, the CPU 22 specifies the value of the network address part of IPca2 using IPca2 and SMdh2 included in the DHCP Offer received from the second DHCP server 70. Then, the CPU 22 selects one candidate IP address (for example, IPca1) including the value of the network address portion that matches the value of the network address portion of the IP address of the terminal device TE.

  Next, in S <b> 26, the CPU 22 broadcasts a Request including the candidate IP address (for example, IPca <b> 1) selected in S <b> 24 to the LAN 4.

  When the DHCP server that has assigned the candidate IP address included in the request of S26 to the printer PR receives the request, it broadcasts an ACK to the LAN 4. The ACK includes the MAC address of the printer PR. Therefore, a device other than the printer PR (for example, the terminal device TE) does not execute a process corresponding to the ACK even when the ACK is received.

  In S28, the CPU 22 monitors reception of ACK. When receiving the ACK, the CPU 22 determines YES in S28, and proceeds to S30.

  In S30, the CPU 22 newly sets the value of the candidate IP address selected in S24 (for example, IPca1) as the IP address of the printer PR, instead of the value of the current IP address of the printer PR (for example, IPpr) ( That is, it is stored in the memory 24). Further, the CPU 22 extracts the DHCP server subnet mask (for example, SMdh1) and the DHCP server IP address (for example, IPdh1) from the received DHCP Offer including the candidate IP address. Then, the CPU 22 newly sets the extracted subnet mask value (for example, SMdh1) instead of the current subnet mask value (for example, SMpr) of the printer PR as the subnet mask of the printer PR, and sets the gateway of the printer PR. Instead of the current gateway address value (for example, IPdh2) of the printer PR, the IP address value (for example, IPdh1) of the extracted DHCP server is newly set as the address. When S30 ends, the process of FIG. 2 ends.

  In FIG. 2, a normal printing process executed by the CPU 22 of the printer PR is not shown. That is, in a state where the terminal device TE and the printer PR belong to the same subnet, the CPU 22 executes normal unicast communication via the gateway and receives a print instruction including print data from the terminal device TE. When the value of the network address portion of the IP address of the terminal device TE matches the value of the network address portion of the IP address of the printer PR, the CPU 22 can receive a print instruction from the terminal device TE. Accordingly, the CPU 22 can receive a print instruction from the terminal device TE, for example, after passing through S30 in FIG. 2 or determining YES in S14.

  When the CPU 22 receives the print instruction from the mobile terminal TE, the CPU 22 executes normal unicast communication via the gateway, transmits a response packet to the print instruction to the mobile terminal TE, and prints the print data included in the print instruction. The image data is supplied to the unit 16 and causes the print execution unit 16 to print the image represented by the print data. Thereafter, the CPU 22 performs normal unicast communication via the gateway and transmits a print completion notification to the terminal device TE.

(Processing executed by the terminal device TE)
Next, with reference to FIG. 4, the contents of the process executed by the CPU 52 of the terminal device TE will be described. The process in FIG. 4 is started when a print instruction including print data is transmitted from the terminal device TE to the printer PR and printing according to the print data has failed in the printer PR. Specifically, the CPU 52 determines that printing has failed in the printer PR when a response packet to the printing instruction is not received from the printer PR even after a predetermined period has elapsed since the printing instruction was transmitted to the printer PR. Then, the process of FIG. 4 is started. More specifically, the situation is as follows.

  The CPU 52 executes name resolution using the node name of the printer PR in the memory 54 when an instruction to execute printing in the printer PR is given from the user. For example, the CPU 52 uses a name resolution server (not shown) or broadcast communication of the printer PR node name stored in the memory 54 to obtain the IP address value (for example, IPpr) of the printer PR. get. Then, the CPU 52 designates the value of the IP address as a transmission destination address, and transmits a print instruction including print data. For example, if the terminal device TE and the printer PR belong to different subnets, the print instruction is not transmitted to the printer PR via the gateway, and therefore the printer PR does not transmit a response packet for the print instruction. In this case, the CPU 52 does not receive a response packet for the print instruction from the printer PR. For example, even if the terminal device TE and the printer PR belong to the same subnet, if the printer PR cannot properly receive a print instruction due to some cause (for example, memory full), the printer The PR does not transmit a response packet for the print instruction. Also in this case, the CPU 52 does not receive a response packet for the print instruction from the printer PR.

  In S <b> 100, the CPU 52 broadcasts a search packet including the node name of the printer PR stored in the memory 54 to the LAN 4. Each device connected to the LAN 4 (that is, the printer PR, the first and second DHCP servers 60 and 70) receives the search packet. Even if a device having a node name that does not match the node name included in the search packet (that is, the first and second DHCP servers 60 and 70) receives the search packet, it does not transmit a response packet to the search packet. On the other hand, when the printer PR having the node name that matches the node name included in the search packet receives the search packet (see YES in S10 of FIG. 2), the printer PR executes unicast communication according to the specific program, and Is transmitted to the terminal device TE (see S12 in FIG. 2).

  In S102, the CPU 52 receives a response packet for the search packet from the printer PR. The response packet includes the current IP address (for example, IPpr) of the printer PR and the current subnet mask (for example, SMpr) of the printer PR.

  In S104, the CPU 52 determines whether or not the value of the network address portion of the IP address (eg, IPte) of the terminal device TE matches the value of the network address portion of the IP address (eg, IPpr) of the printer PR. . Specifically, the CPU 52 uses the IP address (for example, IPte) of the terminal device TE and the subnet mask (for example, SMte) of the terminal device TE stored in the memory 54, and the network address portion of the IP address of the terminal device TE. Value (for example, “192.168.1”) is specified. Further, the CPU 52 uses the value of the printer PR IP address (for example, IPpr) and the value of the subnet mask of the printer PR (for example, SMpr) included in the response packet received in S102 to determine the network address portion of the printer IP address. Is specified (for example, “192.168.100”). Then, the CPU 52 determines whether or not the two specified values match.

  If the CPU 52 determines that the value of the network address part of the IP address of the terminal device TE matches the value of the network address part of the IP address of the printer PR (YES in S104), the process proceeds to S110. On the other hand, if the CPU 52 determines that the value of the network address part of the IP address of the terminal device TE does not match the value of the network address part of the IP address of the printer PR (NO in S104), the process proceeds to S106. move on.

  In S106, the CPU 52 determines whether or not a non-change notification (see S19 in FIG. 2) is received from the printer PR. When the CPU 52 receives a non-change notification from the printer PR, the CPU 52 determines YES in S106, and proceeds to S108. On the other hand, if the CPU 52 has not received a non-change notification from the printer PR, the CPU 52 determines NO in S106 and returns to S100. That is, the CPU 52 broadcasts the search packet to the LAN 4 again.

  In S108, the CPU 52 causes the display unit (not shown) of the terminal device TE to display an error screen indicating that the terminal device TE cannot execute unicast communication of print data with the printer PR. When S108 ends, the process of FIG. 4 ends.

  In S110, the CPU 52 executes unicast communication via the gateway and transmits a print instruction including print data to the printer PR. When S110 ends, the process of FIG. 4 ends.

(Specific case: Figs. 5 and 6)
Next, with reference to FIGS. 5 and 6, the contents of a specific case realized according to the flowcharts of FIGS. 2 and 4 will be described. Case A in FIG. 5 is a case where the user selects to change the IP address of the printer PR. Case B in FIG. 6 is a case where the user selects not to change the IP address of the printer PR. In FIGS. 5 and 6, broadcast communication and unicast communication are indicated by a two-dot chain line and a solid line, respectively.

(Case A; FIG. 5)
In T10, the terminal apparatus TE performs normal unicast communication via the gateway, and transmits a print instruction to the printer PR. The print instruction includes IPpr as the transmission destination address and IPte as the transmission source address. However, since the value of the network address part of IPpr and the value of the network address part of IPte do not match, the first DHCP server 60 that is the gateway of the terminal device TE does not transmit a print instruction to the printer PR. As a result, the printer PR cannot receive a print instruction from the terminal device TE.

  At T12, the terminal apparatus TE determines that printing has failed because it does not receive a response packet to the print instruction from the printer PR even after a predetermined period of time has passed since the print instruction was transmitted (trigger of processing in FIG. 4). ). At T14, the terminal device TE broadcasts a search packet including the node name of the printer PR to the LAN 4 (S100).

  In T16, when the printer PR receives the search packet from the terminal device TE (YES in S10 in FIG. 2), the printer PR executes unicast communication according to the specific program, and sends a response packet including IPpr and SMpr to the terminal device TE. Transmit (S12).

  At T18, when receiving a response packet to the search packet from the printer PR (S102 in FIG. 4), the terminal apparatus TE determines that the value of the network address part of IPpr does not match the value of the network address part of IPte. (NO in S104).

  In T20, the printer PR determines that the value of the IPte network address part does not match the value of the IPpr network address part (NO in S14 of FIG. 2). At T22, the printer PR displays a selection screen (FIG. 3) (S16). At T24, the user selects to change IPpr on the selection screen (YES in S18). In T26, the printer PR broadcasts DHCP Discover to the LAN 4 (S20).

  In T28, when receiving the DHCP Discover, the first DHCP server 60 broadcasts a DHCP Offer including IPca1 “192.168.1.3”, SMdh1, and IPdh1 to the LAN 4. In T30, when receiving the DHCP Discover, the second DHCP server 70 broadcasts a DHCP Offer including IPca2 “192.168.100.3”, SMdh2, and IPdh2 to the LAN 4.

  In T31, when the printer PR receives two DHCP Offers, the printer PR sets the value of the network address part that matches the value of the network address part of IPte from the two candidate IP addresses included in the two DHCP Offers. A candidate IP address to be included (that is, IPca1) is selected (S24 in FIG. 2). Next, in T32, the printer PR broadcasts a request including IPca1 to the LAN 4 (S26).

  At T34, when the second DHCP server 70 receives the request, the second DHCP server 70 broadcasts ACK to the LAN 4.

  In T36, when receiving the ACK (YES in S28 of FIG. 2), the printer PR sets IPca1 instead of IPpr as the IP address of the printer PR (S26). Further, the printer PR newly sets SMdh1 instead of SMpr as the subnet mask of the printer PR. Further, the printer PR newly sets IPdh1 instead of IPdh2 as the gateway address of the printer PR. That is, the gateway of the printer PR is changed from the second DHCP server 70 to the first DHCP server 60.

  At T40, the terminal device TE broadcasts again a search packet including the node name of the printer PR to the LAN 4 (S100 in FIG. 4). Although not shown, the terminal device TE and the printer PR repeatedly execute the same processing as T14 to T18 between T18 and T40.

  In T42, when the printer PR receives the search packet from the terminal device TE again (YES in S10 in FIG. 2), the printer PR performs unicast communication according to the specific program and sends a response packet including IPca1 and SMdh1 to the terminal device TE. (S12). Next, in T44, the printer PR determines that the value of the network address part of IPte matches the value of the network address part of IPca1 (YES in S14).

  In T46, when the terminal device TE receives a response packet to the search packet from the printer PR (S102 in FIG. 4), it determines that the value of the network address part of IPca1 matches the value of the network address part of IPte ( YES in S104). Next, at T48, the terminal apparatus TE performs normal unicast communication via the gateway, and transmits a print instruction to the printer PR (S110). The print instruction includes IPca1 as the transmission destination address and IPte as the transmission source address. Since the value of the network address part of IPca1 matches the value of the network address part of IPte, the first DHCP server 60, which is the gateway of the terminal apparatus TE, transmits a print instruction to the printer PR.

  In T50, when the printer PR receives a print instruction from the terminal device TE, the printer PR prints an image represented by the print data. Thereafter, although not shown, the printer PR performs normal unicast communication via the gateway, and transmits a print completion notification to the terminal device TE.

(Case B; FIG. 6)
In this case, the description will focus on the differences from Case A. T10 to T22 are the same as those in FIG. At T100, the user selects not to change IPpr on the selection screen (NO in S18 of FIG. 2). In this case, in T102, the printer PR performs unicast communication according to the specific program and transmits a non-change notification to the terminal device TE (S19).

  In T104, when receiving a non-change notification from the printer PR (YES in S106 of FIG. 4), the terminal device TE displays an error screen (S108). In this case, unlike the case A in FIG. 5, the terminal device TE does not broadcast the search packet to the LAN 4 again (that is, does not execute S100 in FIG. 4).

(Effects of the first embodiment)
As shown in FIG. 5, the printer PR receives the search packet broadcast from the terminal device TE (T14), transmits a response packet to the terminal device TE (T16), the value of the network address part of IPte, It is determined whether or not the value of the network address part of IPpr matches (T20). When the printer PR determines that the value of the network address part of IPte does not match the value of the network address part of IPpr, the value of the network address part of IPte is used instead of IPpr as the IP address of the printer PR. IPca1 including the value of the network address part that coincides with is newly set (T36). Then, the printer PR receives again the search packet broadcast from the terminal device TE to the LAN 4 (T40), and transmits a response packet including IPca1 to the terminal device TE (T42). That is, the printer PR can notify the terminal device TE of the IPca1 newly set in the printer PR. Accordingly, the terminal device TE can know that IPca1 is newly set in the printer PR, that is, that normal unicast communication via the gateway can be executed with the printer PR, and print data can be obtained. Send to printer PR. As a result, the printer PR performs unicast communication of print data using IPca1 with the terminal device TE (T48). In other words, the printer PR can appropriately eliminate the event that cannot be executed with the terminal device TE for the unicast communication of the print data, and can appropriately execute the unicast communication of the print data with the terminal device TE.

  In case A of FIG. 5, since the user selects to change IPpr on the selection screen (T24), the printer PR newly sets IPca1 instead of IPpr as the IP address of the printer PR. (T36). On the other hand, as shown in case B of FIG. 6, when the user selects not to change IPpr on the selection screen (T100), the printer PR transmits a non-change notification to the terminal device TE. (T102), the IP address of the printer PR is not changed. In this case, although unicast communication of print data cannot be performed between the printer PR and the terminal device TE, the printer PR uses other devices (for example, the terminal device) connected to the LAN 4 using IPpr. Unicast communication with a terminal device different from TE) can be executed. Thus, in this embodiment, the printer PR can appropriately switch whether or not to change the IP address of the printer PR according to the user's selection.

(Correspondence)
The printer PR and the terminal device TE are examples of “first communication device” and “second communication device”, respectively. The first and second DHCP servers 60 and 70 are examples of the “IP address assignment server”. In FIG. 5, the search packet of T14, the response packet of T16, and the response packet of T42 are examples of “request packet”, “first response packet”, and “second response packet”, respectively. IPpr, SMpr, IPte, and SMte are examples of “current IP address value”, “current subnet mask value”, “target IP address value”, and “target subnet mask value”, respectively. IPca1 is an example of a value of “new IP address” and a value of “one candidate IP address”. IPca1 and IPca2 are examples of the value of “two or more candidate IP addresses”. The value of the network address part of IPpr and the value of the network address part of IPte are examples of “current network address value” and “target network address value”, respectively. The print data is an example of “target data”.

  In FIG. 2, the processing of S10, the processing of S12, the processing of S14, and the processing of S16 are respectively “request packet reception unit”, “response packet transmission unit”, “determination unit (or second determination unit)”, It is an example of processing executed by the “display control unit”. The processing of S20 and S22 is an example of processing executed by the “candidate IP address receiving unit”. The processing of S24 and S30 is an example of processing executed by the “setting unit”.

  In FIG. 4, the processing of S100, the processing of S102, and the processing of S104 are examples of processing executed by the “request packet transmission unit”, “response packet reception unit”, and “first determination unit”, respectively.

(Second embodiment; FIGS. 7 and 8)
In the present embodiment, a method for changing the IP address of the printer PR is different from that in the first embodiment. With reference to FIG. 7, the contents of the process executed by the CPU 22 of the printer PR will be described. The processes of S10 to S19 are the same as those in FIG.

  In S200, the CPU 22 determines the value of the candidate IP address and the value of the candidate subnet mask. Specifically, first, the CPU 22 determines the network address specified in S14 out of the IP address value (for example, “192.168.1.2”) of the terminal device TE included in the search packet received in S10. The value (for example, “192.168.1.11”) of the candidate IP address is changed at random by changing the value (for example, “2”) of the host part that is a part other than the part (for example, “192.168.8.1”) ). That is, the CPU 22 determines a candidate IP address without using the DHCP servers 60 and 70. Further, the CPU 22 determines the subnet mask value of the terminal device TE included in the search packet received in S10 as the candidate subnet mask value. In the modification, for example, the CPU 22 may store an IP address previously set as the IP address of the printer PR in the memory 24, or may determine the IP address as the value of the candidate IP address. Good.

  In S202, the CPU 22 broadcasts a request including the IPre determined in S200 to the LAN 4. The Request is a packet for requesting the DHCP servers 60 and 70 to use IPre.

  When a DHCP server (for example, the first DHCP server 60) capable of assigning IPre included in the request in S202 receives the request, it checks whether or not IPre is currently assigned to another device. Then, the DHCP server broadcasts ACK to the LAN 4 when it is confirmed that IPre is not currently assigned to another device.

  In S204, the CPU 22 monitors reception of ACK. When receiving the ACK, that is, when permission to use IPre is obtained, the CPU 22 determines YES in S204, and proceeds to S206. Although not shown in the figure, the CPU 22 ends the process of FIG. 7 when ACK is not received, that is, when IPre is currently assigned to another device.

  In S206, the CPU 22 newly sets the value IPre of the candidate IP address determined in S200, instead of the current IP address value (eg, IPpr) of the printer PR, as the IP address of the printer PR (ie, the memory). 24). Further, the CPU 22 newly sets the value of the candidate subnet mask determined in S200 as the subnet mask of the printer PR, instead of SMpr. The ACK received in S204 includes the value of the IP address of the DHCP server that is the transmission source of the ACK. The CPU 22 newly sets the IP address value of the DHCP server that is the transmission source of the ACK instead of the current gateway address value as the gateway address of the printer PR. That is, the gateway of the printer PR is changed. When S206 ends, the process of FIG. 7 ends.

(Specific case; Fig. 8)
Next, with reference to FIG. 8, the contents of a specific case realized according to the flowchart of FIG. 7 will be described. T10 to T24 are the same as in FIG.

  In T200, the printer PR changes the value of the host part of the IPte included in the response packet received in T14 to determine the value IPre “192.168.1.11” of the candidate IP address, and SMte included in the response packet received at T14 is determined as the value of the candidate subnet mask (S200 in FIG. 7). T202 and T204 are the same as T32 and T34 in FIG. 5 except that the value of the candidate IP address is IPre.

  In T206, when receiving the ACK (YES in S204), the printer PR sets IPre instead of IPpr as the IP address of the printer PR (S206). The printer PR newly sets SMte instead of SMpr as the subnet mask of the printer PR. Further, the printer PR newly sets IPdh1 included in the ACK of T204, instead of IPdh2, as the gateway address of the printer PR. That is, the gateway of the printer PR is changed from the second DHCP server 70 to the first DHCP server 60. T210 to T220 are the same as T40 to T50 in FIG. 5 except that the value of the IP address newly set in the printer PR is IPre.

(Effect of the second embodiment)
As shown in FIG. 8, the printer PR determines IPre including the value of the network address part that matches the value of the network address part of IPte based on IPte (T200). Then, the printer PR newly sets IPre instead of IPpr as the IP address of the printer PR (T206). As a result, the printer PR can appropriately execute unicast communication of print data using IPre with the terminal device TE (T218). In particular, in the present embodiment, the printer PR does not need to perform communication of DHCP Discover and DHCP Offer, so that the communication load can be reduced. In this embodiment, IPre is an example of a value of “candidate IP address” and a value of “new IP address”. In FIG. 7, the processes of S <b> 200 to S <b> 206 are an example of processes executed by the “setting unit”.

(Third embodiment)
In the present embodiment, a method for changing the IP address of the printer PR is different from that in the first embodiment. The printer PR can switch the IP address setting method of the printer PR between the DHCP method and the STATIC method. The DHCP method is a method for the printer PR to set the IP address assigned from the DHCP server as the IP address of the printer PR itself. The STATIC method is a method for the printer PR to set an IP address designated by the user as the IP address of the printer PR itself without using a DHCP server.

(Processing executed by printer PR; FIG. 9)
With reference to FIG. 9, the contents of the process executed by the CPU 22 of the printer PR will be described. The processes of S10 to S19 are the same as those in FIG.

  In S300, the CPU 22 determines a candidate IP address value, a candidate subnet mask value, and a candidate gateway address value. Specifically, the CPU 22 displays a screen for prompting specification of these values on the display unit 14, and sets the IP address value, subnet mask value, and gateway address value specified by the user, respectively. The candidate IP address value, candidate subnet mask value, and candidate gateway address value are determined. Hereinafter, the value of the candidate IP address, the value of the candidate subnet mask, and the value of the candidate gateway address determined here are referred to as “IPui”, “SMui”, and “GWui”, respectively.

  In S302, the CPU 22 broadcasts the ARP packet including the IPui determined in S300 to the LAN 4.

  In S304, the CPU 22 monitors whether a response packet for the ARP packet is received. When the IPui included in the ARP packet is currently set in another device connected to the LAN 4, the other device transmits a response packet to the ARP packet to the printer PR. When receiving the ARP packet (YES in S304), the CPU 22 ends the process of FIG. In the modified example, when receiving the ARP packet (YES in S304), the CPU 22 may return to S300 and prompt the user to specify another IP address. On the other hand, when the IPui included in the ARP packet is not set in any device connected to the LAN 4, the CPU 22 does not receive a response packet for the ARP packet. When the CPU 22 does not receive a response packet for a predetermined period after transmitting the ARP packet in S302, the CPU 22 determines NO in S304 and proceeds to S305.

  In S305, the CPU 22 determines whether or not the current IP address setting method of the printer PR is the DHCP method. If the current IP address setting method of the printer PR is the DHCP method, the CPU 22 determines YES in S305, and changes the IP address setting method of the printer PR from the DHCP method to the STATIC method in S306. On the other hand, if the current IP address setting method of the printer PR is the STATIC method, the CPU 22 determines NO in S305, skips S306, and proceeds to S308.

  In S308, the CPU 22 newly sets the value IPui of the candidate IP address determined in S300, instead of the current IP address value (eg, IPpr) of the printer PR, as the IP address of the printer PR (ie, the memory). 24). Further, the CPU 22 newly sets the value SMui of the candidate subnet mask determined in S300 instead of SMpr as the subnet mask of the printer PR, and sets the candidate gateway address determined in S300 as the gateway address of the printer PR. A value GWui is newly set. When S308 ends, the process of FIG. 9 ends.

(Specific case; Fig. 10)
Next, with reference to FIG. 10, the contents of a specific case realized according to the flowchart of FIG. 9 will be described. T10 to T24 are the same as in FIG. In the initial state of FIG. 10, the IP address setting method of the printer PR is the DHCP method, and an IP address (that is, IPpr) is assigned from the first DHCP server 60 to the printer PR.

  In T300, the printer PR determines IPui, SMui, and GWui designated by the user as a candidate IP address value, a candidate subnet mask value, and a candidate gateway address value, respectively (S300 in FIG. 9). In this case, in T300, the IPi “192.168.1.21” including the value of the network address portion that matches the value of the network address portion of IPte is designated by the user. Also, SMui that matches SMte is specified by the user, and GWui that matches the value IPdh1 of the IP address of the first DHCP server 60 that is the gateway of the terminal device TE is specified by the user. Next, in T302, the printer PR broadcasts an ARP packet including IPui to the LAN 4 (S302).

  IPui is not set in any device connected to the LAN 4. Therefore, in T304, the printer PR does not receive a response packet for the ARP packet (NO in S304).

  In T306, the printer PR determines that the IP address setting method of the printer PR is the DHCP method (YES in S305), and changes the IP address setting method of the printer PR from the DHCP method to the STATIC method (S306).

  In T308, the printer PR sets IPui instead of IPpr as the IP address of the printer PR (S308). The printer PR newly sets SMui instead of SMpr as the subnet mask of the printer PR. Further, the printer PR newly sets GWui as the gateway address of the printer PR, instead of IPdh2.

  T312 to T322 are the same as T40 to T50 in FIG. 5 except that the value of the IP address newly set in the printer PR is IPui.

(Effect of the third embodiment)
As shown in FIG. 10, the printer PR determines an IPui that includes the value of the network address portion that matches the value of the network address portion of IPte based on the designation by the user (T300). Then, the printer PR newly sets IPui instead of IPpr as the IP address of the printer PR (T308). As a result, the printer PR can appropriately execute unicast communication of print data using IPui with the terminal device TE (T320). In particular, in the present embodiment, the printer PR does not need to perform communication of DHCP Discover and DHCP Offer, so that the communication load can be reduced. In this embodiment, IPui is an example of the value of “new IP address”. In FIG. 9, the process of S308 is an example of a process executed by the “setting unit”.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The modifications of the above embodiment are listed below.

(Modification 1) In FIG. 2, the processing of S16, S18, and S19 may not be executed. That is, if the value of the network address part of the IP address of the terminal device TE and the value of the network part of the IP address of the printer PR do not match (NO in S14 of FIG. 2), the CPU 22 of the printer PR The IP address may be changed. That is, the “first communication apparatus” may not include the “display control unit” and the “notification transmission unit”.

(Modification 2) In the first embodiment described above, the communication system 2 includes two DHCP servers, a first DHCP server 60 and a second DHCP server 70. The number of DHCP servers provided in the communication system 2 is not limited to two, and may be any number as long as it is one or more. For example, it is assumed that the communication system 2 includes only the first DHCP server 60 and does not include the second DHCP server 70. Further, the IP address of the printer PR is set to the value IPpr specified by the user according to the STATIC method, and the IP address assigned by the first DHCP server 60 is assigned to the IP address of the terminal device TE according to the DHCP method. Assume the situation set in. Even in such a situation, an event may occur in which the value of the network address part of IPpr does not match the value of the network address part of IPte. In this case, the CPU 22 of the printer PR may acquire a new IP address from the first DHCP server 60 and set the value of the new IP address as the IP address of the printer PR instead of IPpr.

(Modification 3) The communication system 2 may not include a DHCP server. Then, the IP address of the printer PR is set to the value IPpr specified by the user according to the STATIC method, and the IP address of the terminal device TE is set to the value IPte specified by the user according to the STATIC method. Assume the situation. Even in such a situation, an event may occur in which the value of the network address part of IPpr does not match the value of the network address part of IPte. In this case, the CPU 22 of the printer PR determines a new IP address in accordance with the STATIC method, and sets the value of the new IP address instead of IPpr as the IP address of the printer PR, as in the third embodiment. May be.

(Modification 4) In each of the above embodiments, the “first communication device” and the “second communication device” are the printer PR and the terminal device TE, respectively. In the modification, for example, the “first communication device” and the “second communication device” may be the scanner and the terminal device TE, respectively. In this case, the “target data” may be scan data. The “first communication device” is not limited to a printer and a scanner, and may be, for example, a multi-function device, a copier, a FAX, a telephone, a PDA, a mobile phone, a server, or the like. In another modification, the “second communication device” is not limited to the terminal device TE, and may be, for example, a printer, a scanner, a multi-function device, a copier, a FAX, a telephone, a server, or the like.

(Modification 5) In each of the above-described embodiments, the CPU 22 of the printer PR and the CPU 52 of the terminal device TE execute programs (that is, software), thereby realizing the processes shown in FIGS. Instead, at least one of the processes in FIGS. 2 to 10 may be realized by hardware such as a logic circuit.

  The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

  2: communication system, 4: LAN, 12: operation unit, 14: display unit, 16: network I / F, 20, 50: control unit, 22, 52: CPU, 24, 54: memory, 60: first DHCP server, 70: second DHCP server, TE: terminal device, PR: printer, IPpr: IP address value of printer PR, IPte: IP address value of terminal device TE, IIPca1: candidate IP address value

Claims (8)

A first communication device comprising:
A request packet receiver for receiving a request packet broadcast to a local area network from a second communication device different from the first communication device, wherein the request packet is a current IP address of the second communication device; A request packet receiving unit including a target IP address that is an address and a target subnet mask that is a current subnet mask of the second communication device;
A response packet transmitting unit configured to transmit a first response packet to the request packet to the second communication device via the local area network when the request packet is received from the second communication device; The first response packet includes a current IP address that is a current IP address of the first communication device and a current subnet mask that is a current subnet mask of the first communication device. A response packet transmitter,
When the request packet is received from the second communication device, the value of the network address portion of the target IP address using the value of the target IP address and the value of the target subnet mask included in the request packet The target network address value is specified, and the current network address value that is the value of the network address portion of the current IP address is specified using the value of the current IP address and the value of the current subnet mask. A determination unit for determining whether or not the target network address value matches the identified current network address value;
When it is determined that the target network address value does not match the current network address value, a network that matches the target network address value instead of the current IP address as the IP address of the first communication device A setting section for setting a new IP address including the value of the address section;
After the new IP address is set as the IP address of the first communication device, unicast communication of target data using the new IP address is executed with the second communication device via the local area network. A unicast communication execution unit,
The request packet receiver further re-transmits the request packet broadcast again from the second communication device to the local area network after the new IP address is set as the IP address of the first communication device. Receive
The response packet transmitting unit further includes a second response packet for the request packet via the local area network when the request packet is received again from the second communication device, Transmitting the second response packet including an IP address to the second communication device;
The unicast communication execution unit transmits the unicast communication of the target data using the new IP address via the local area network after the second response packet is transmitted to the second communication device. With the second communication device,
First communication device. The first communication device further includes:
A selection screen for allowing the user to select whether or not to change the IP address of the first communication device when it is determined that the target network address value does not match the current network address value; A display control unit for displaying on the display unit of the communication device of 1,
The setting unit
When it is selected to change the IP address of the first communication device on the selection screen, the new IP address is set instead of the current IP address as the IP address of the first communication device. ,
When it is selected not to change the IP address of the first communication device on the selection screen, the new IP address is not set instead of the current IP address as the IP address of the first communication device. The first communication device according to claim 1.   The setting unit, as the IP address of the first communication device, replaces the current IP address with the new IP assigned by an IP address assignment server different from the first communication device and the second communication device. The 1st communication apparatus of Claim 1 or 2 which sets an address. The first communication device further includes:
When it is determined that the target network address value does not match the current network address value in a state where two or more IP address assignment servers are connected to the local area network, the two or more IP addresses A candidate IP address receiving unit that requests each of the allocation servers to allocate an IP address to the first communication device and receives two or more candidate IP addresses from each of the two or more IP address allocation servers. Prepared,
The setting unit includes one candidate IP address including a value of a network address portion that matches the target network address value from two or more candidate IP addresses received from the two or more IP address assignment servers. The first communication apparatus according to claim 3, wherein the new IP address that is the one candidate IP address is determined by selecting. The setting unit
If it is determined that the target network address value and the current network address value do not match, a candidate IP address including a value of the network address portion that matches the target network address value without using an IP address assignment server Decide
The IP address allocation server different from the first communication device and the second communication device is requested to use the candidate IP address, and permission to use the candidate IP address is acquired from the IP address allocation server. In this case, the first communication device according to claim 1 or 2, wherein the candidate IP address is determined as the new IP address. A communication system comprising a first communication device and a second communication device,
The second communication device is:
A request packet transmitter for broadcasting a request packet to a local area network to which the first communication device and the second communication device are connected, wherein the request packet is a current packet of the second communication device. The request packet transmitter including a target IP address that is an IP address and a target subnet mask that is a current subnet mask of the second communication device;
A response packet receiving unit that receives a first response packet to the request packet from the first communication device via the local area network, wherein the first response packet is the first communication device. A response packet receiving unit, including: a current IP address that is a current IP address of the first communication device; and a current subnet mask that is a current subnet mask of the first communication device;
A target that is the value of the network address portion of the target IP address using the value of the target IP address and the value of the target subnet mask when the first response packet is received from the first communication device; A network address value is specified, and a current network address value that is a value of a network address portion of the current IP address is determined using the value of the current IP address and the value of the current subnet mask included in the first response packet. A first determination unit that determines whether the specified target network address value and the specified current network address value match, and
The request packet transmitting unit further broadcasts the request packet to the local area network again when the first determination unit determines that the target network address value does not match the current network address value. ,
In the response packet receiving unit, a new IP address including a value of the network address part matching the target network address value is set as the IP address of the first communication device instead of the current IP address Later, from the first communication device, the second response packet, which is the second response packet to the request packet broadcast again via the local area network, including the new IP address is received. ,
The first communication device is:
A request packet receiver for receiving the request packet broadcast from the second communication device to the local area network;
A response packet transmitter configured to transmit the first response packet to the request packet to the second communication device via the local area network when the request packet is received from the second communication device; ,
When the request packet is received from the second communication device, the target network address value is identified using the value of the target IP address and the value of the target subnet mask included in the request packet, The current network address value is identified using the current IP address value and the current subnet mask value, and whether or not the identified target network address value and the identified current network address value match. A second determination unit for determining;
When the second determination unit determines that the target network address value does not match the current network address value, the IP address of the first communication device is replaced with the new IP address instead of the current IP address. A setting unit for setting an IP address;
After the new IP address is set as the IP address of the first communication device, unicast communication of target data using the new IP address is executed with the second communication device via the local area network. A unicast communication execution unit,
The request packet receiver further re-transmits the request packet broadcast again from the second communication device to the local area network after the new IP address is set as the IP address of the first communication device. Receive
The response packet transmitting unit further includes a second response packet for the request packet via the local area network when the request packet is received again from the second communication device, Transmitting the second response packet including an IP address to the second communication device;
The unicast communication execution unit transmits the unicast communication of the target data using the new IP address via the local area network after the second response packet is transmitted to the second communication device. A communication system that executes the second communication apparatus with the second communication apparatus. The first communication device further includes:
A selection screen for allowing the user to select whether or not to change the IP address of the first communication device when it is determined that the target network address value does not match the current network address value; A display control unit to be displayed on the display unit of the first communication device;
A notification transmitter for transmitting a predetermined notification to the second communication device via the local area network when it is selected not to change the IP address of the first communication device on the selection screen; With
When the predetermined notification is received from the first communication device, the request packet transmission unit of the second communication device receives the first network address value and the current network address value if they do not match. The communication system according to claim 6, wherein the request packet is not broadcast again to the local area network even if determined by one determination unit. A computer program for a first communication device, comprising:
In the computer mounted on the first communication device, the following processes, that is,
A request packet reception process for receiving a request packet broadcast to a local area network from a second communication device different from the first communication device, wherein the request packet is a current IP address of the second communication device. A request packet reception process including a target IP address that is an address and a target subnet mask that is a current subnet mask of the second communication device;
Response packet transmission processing for transmitting a first response packet to the request packet to the second communication device via the local area network when the request packet is received from the second communication device. The first response packet includes a current IP address that is a current IP address of the first communication device and a current subnet mask that is a current subnet mask of the first communication device. Response packet transmission processing,
When the request packet is received from the second communication device, the value of the network address portion of the target IP address using the value of the target IP address and the value of the target subnet mask included in the request packet The target network address value is specified, and the current network address value that is the value of the network address portion of the current IP address is specified using the value of the current IP address and the value of the current subnet mask. A determination process for determining whether or not the target network address value matches the specified current network address value;
When it is determined that the target network address value does not match the current network address value, a network that matches the target network address value instead of the current IP address as the IP address of the first communication device A setting process for setting a new IP address including the value of the address part;
After the new IP address is set as the IP address of the first communication device, unicast communication of target data using the new IP address is executed with the second communication device via the local area network. Unicast communication execution processing to be executed,
In the request packet receiving process, after the new IP address is set as the IP address of the first communication device, the request packet broadcast again from the second communication device to the local area network is again transmitted. Receive
In the response packet transmission process, when the request packet is received again from the second communication device, the response packet transmission process is a second response packet to the request packet via the local area network, Sending the second response packet including an IP address;
In the unicast communication execution process, after the second response packet is transmitted to the second communication device, the unicast communication of the target data using the new IP address via the local area network With the second communication device,
Computer program.

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