JPH03235546A - Data communication system - Google Patents

Abstract

PURPOSE:To continue the communication between a host computer and a terminal equipment without hindrance by selecting and using other terminal controller when system-down of the terminal controller and a communication line currently in operation is recognized. CONSTITUTION:While an AP(application program) 14 and an AP 44 are in communication, when a terminal controller 2 is in system-down due to any fault, a down-detection section 12 recognizing the fault informs the system-down of the terminal controller 12 to a communication line changeover section 13 and the communication line changeover section 13 reads the content of a communication parameter file 16 of an external storage device 15. A communication parameter for the terminal controller 3 being a changeover destination communication repeater at a fault state is stored in the communication parameter file 16 and the communication line changeover section 13 relays the terminal controller 3 to the communication control section 11 according to the information to give a command of connection to the host computer 4. Thus, the AP-AP communication between the terminal equipment 1 and the host computer 4 is continued without intermission.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a communication system in which a host computer and a terminal device are connected using a communication relay function of a terminal control device, and in particular, the present invention relates to a communication system in which a host computer and a terminal device are connected using a communication relay function of a terminal control device, and in particular, The present invention relates to a data communication method that detects a terminal control device and transfers the communication relay function to another terminal control device.

[Conventional technology]

Conventionally, in data communication systems, when a terminal control device serving as a communication relay device or a communication line goes down due to some kind of failure, data communication between the host computer and the terminal device is interrupted until the terminal control device or communication line is restored. This caused irreversible damage.

[Problem to be solved by the invention]

In the conventional data communication method described above, there is only one terminal control device that serves as a communication relay device in one communication system, and the terminal control device and the terminal device are connected in a tightly coupled relationship. If a line goes down, you have to wait for the communication line to be restored, and if a terminal control device goes down, you have to restart not only the terminal control device but also the terminal device, and then restart the communication line. This has the disadvantage that it also affects other terminal devices that do not perform this function.

[Means to solve the problem]

The data communication system of the present invention includes: a plurality of terminal devices; a plurality of terminal control devices connected to the terminal devices via a bus-type communication line; a host computer connected to the terminal control device via a communication line; It has a means for monitoring the operating status of each other when the terminal device and the host computer are transferring data using the communication relay function of the terminal control device, and it is possible to detect when the terminal control device and the communication line currently in operation are down. When recognized, another terminal control device is switched to use, and communication between the host computer and the terminal device continues without any trouble.

〔Example〕

Next, the present invention will be explained with reference to the seventh page.

FIG. 1 is a system configuration diagram of an embodiment of the present invention.

Now, assume that the terminal device 1 and the host computer 4 are communicating normally. The terminal device 1 is connected to a terminal control device 2 and a terminal control device N3 via a bus-type communication line, and is further connected to a host computer 4 via a communication line 6 and a communication line 7, respectively. Application program on terminal device 1 (hereinafter referred to as AP)
The communication data from 14 is relayed by the communication relay unit 23 on the terminal control device 2 via the bus-type communication line 5 under the control of the communication control unit 11, and then passes through the communication control unit 21 again and via the communication line 6. , reaches the AP 44 through the communication control unit 41 on the host computer 4. For downlink data, take the opposite route.

When the AP 14 and the AP 44 are communicating through the above route, the communication between the down detection unit 12 on the terminal device 1 and the down detection notification unit 22 on the terminal control device 2 and the host computer 1
Monitoring data for detecting down of each device is exchanged between the down detection unit 42 on the top and the down detection notification unit 22 on the terminal control device 2 via the bus type communication line 5 and the communication line 6, respectively. has been done. In other words, the down detection unit 12 is a terminal device! The down detection notification unit 22 notifies the host computer 4 that the terminal control device 2 is operating normally.
Down detection unit 1 confirms that the communication channel with
Notify 2. Similarly, the down detection unit 42 informs the down detection notification unit 2 that the host computer 4 is operating normally.
2, and the down detection notification section 22 notifies the down detection section 42 of the normal notification received from the down detection section 12 on the terminal device 1.

The down detection units 12 and 42 confirm that communication between the terminal device 1 and the host computer 4 is being performed normally as described above. This is recognized by three parties including the down detection notification section 22. This system monitors the status of the communication line and each device by notifying each other of this monitoring data at regular intervals.

Now, let us consider a case where the terminal control device 2 goes down due to some kind of failure. At this time, since the down detection notification section 22 on the terminal control device 2 cannot respond to the monitoring data output from the down detection section 12 on the terminal device 1, the down detection section 12 waits for a response for a certain period of time. The monitoring data is sent out again, and when there is no response after repeating this a certain number of times, it is recognized that the terminal control device 2 is down. Similarly, the host computer 4 also recognizes that the terminal control device 2 is down.

Recognizing the failure, the down detection section 12 notifies the communication line switching section 13 that the terminal control device 2 is down, and upon receiving this, the communication line switching section 13 reads the contents of the communication parameter file 16 on the external storage device 15 . The communication parameter file 16 stores communication parameters for the terminal control device 3, which becomes the switching optical communication relay device in the event of a failure, and according to this information, the communication line switching unit 13 relays the terminal control device 3 to the communication control unit 11. and issues a command to connect with the host computer 4.

At this time, the down detection unit 42 on the host computer 4 similarly notifies the communication line switching unit 43 of the failure, and updates the communication parameters of the alternative terminal control device at the time of failure in the communication parameter file 46 on the external storage device 45. It is passed to the communication control unit 41. The communication control unit 41 uses this information to
After switching the connection between the communication line 6 and the logical (physical) communication line from the communication line 6 to the communication line 7, and confirming the normality of each other by the down detection unit 12 and the down detection notification unit 32, the connection between the AP 14 and the AP 44 is changed. Resume data communication.

However, the fact that the terminal control device 2 was switched to the terminal control device 3 is AP14. '44 is not notified, and the terminal operator can continue his work without knowing about the failure of the communication relay equipment. Even if this terminal control device 3 goes down, as long as other terminal control devices are operating normally or the terminal control device 2 is restored, switching will be performed without limit, and the AP14 and AP44
Open data communication is guaranteed.

Next, the terminal device 1. Terminal control device 2. A description will now be given of the failure of the communication line 6 when the host computer 4 is communicating. At this time, the down detection notification section 22 is notified by the communication control section 21 that the communication line 6 is down. The down detection notification section 22 transmits this line down information to the down information detection section]2. On the other hand, the down detection unit 42 is notified by the communication control unit 41 that the communication line 6 is down, and the communication relay device is switched in the same way as when the terminal control device 2 goes down, and data communication between the AP 14 and the AP 44 is guaranteed. Ru. Here, the communication line down means, for example, the packet line goes down, and the failure notification is sent to the communication control unit 2.
1 or 41 is recognized, and the down detection notification section 22 or the down detection section 42 is notified.

Next, the terminal device 1. Host computer 4 when communicating between terminal control device 2 and host computer 4
Explain about down. When the host computer 4 goes down, the down detection notification section 22 recognizes that the host computer 4 is down because monitoring data is not sent from the host computer 4 for a certain period of time. At this time, the down detection notification section 22 notifies the down detection section 12 that the host computer 4 is down, and makes it aware that data communication with the host computer 4 is impossible even if the terminal control device is switched. Therefore, only in this case, the down detection unit 12 notifies the AP 14 of the failure, and
terminates data communication and waits for the host computer 4 to recover.

When a communication line goes down, the communication control section monitors the line, and when a terminal device, terminal control device, and host computer go down, it is done by exchanging monitoring data between the down detection (notification) sections. Therefore, since these down states can be distinguished, the terminal control device can be switched only when the communication line and the terminal control device are down.

〔Effect of the invention〕

As explained above, the present invention includes a plurality of communication relay devices (terminal control devices) in one communication system, and the communication relay devices (terminal control devices) and the terminal devices are connected by a bus-type communication line. Since there is a loosely coupled relationship, the terminal control device (
Even if the communication relay device (communication relay device) or the communication line goes down, it is possible to switch to another terminal control device as the communication relay device and continue the AP-AP communication between the terminal device and the host computer without interruption. It's effective.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of the present invention. 1...Terminal device, 2.3...Terminal control device, 4...
- Host computer, 5... bus type communication line, 6.
7...Communication line.

Claims (1)

[Claims] A plurality of terminal devices, a plurality of terminal control devices connected to the terminal devices via a bus-type communication line, a host computer connected to the terminal control device via a communication line, and a communication relay function of the terminal control device. The terminal device and the host computer have means for monitoring each other's operating status when they are transferring data, and when it is recognized that the currently operating terminal control device and communication line are down, another terminal control device is activated. A data communication method that uses switching to continue communication between a host computer and a terminal device without any hindrance.