IES79079B2

IES79079B2 - A communication system for facilitating communication between a PC and a host computer

Info

Publication number: IES79079B2
Authority: IE
Inventors: John Anthony Dolan; Darrell John Hooper; Zafar Iqbal Hayat; David Roy Williams
Original assignee: Openwrite Limited
Priority date: 1997-08-20
Filing date: 1997-08-20
Publication date: 1998-04-08
Also published as: IES970617A2; GB9818130D0; GB2329734A; GB2329734B

Abstract

An object-oriented system for facilitating communication between a PC operating in a PC-compatible environment and a host computer operating in a non-PC-compatible environment permits the selection and accessing of data in the host computer by the PC. Resident in the PC are an object 11, which takes possession of a communications port of the PC for passing bit-streams between the PC and the host computer, and a logon-to-host object 12. Resident in the host computer are an object 13 which translates PC requests into host-executable procedures, a host-procedure-processor object 14, an object 15 for data selection and acquisition, an object 17 for managing host-resident databases, and an object 16 which provides compression and redundancy-elimination in acquired data to be sent to the PC.

Description

A communication system for facilitating communication between a PC and a host computer The present invention relates to a communication system for facilitating communication between a PC and a host computer wherein the PC operates in a PC compatible environment, and the host computer operates in a non-PC compatible environment.

Due to the power and functionality of desk top computers, for example, PC's, it is rapidly becoming essential that PC's which operate in a PC environment should be able to communicate directly with a host computer operating in a non-PC environment, for example, a Digital VAX/VMS environment, a Hewlett Packard MPE environment, and/or an IBM MVS environment.

In particular, it is desirable that a PC which is a single process/single user computer should be able to communicate with a host computer which is a multiuser/multi-process computer.

Broadly speaking, two types of communication systems are known for communicating a PC operating in a PC compatible environment and a host computer operating in a non-PC compatible environment. One such communication system is generally referred to as a terminal emulation and connectivity system, while the other is generally referred to as an open database connectivity system. In the terminal emulation and connectivity system, software is available which is made resident in the PC which enables the PC to connect to the host computer, emulate the functions of the host computer, and transfer data files in various predetermined formats between the PC and the host computer. In general, such software is windows based software. However, this system does not give the user of the PC a means for selecting, filtering or sorting the data to be transferred, it merely allows the user to transfer predetermined, pre-selected data. The preselection of the data is carried out on the host computer under the control of special purpose software which permits communication between the terminal emulation and connectivity software resident in the PC. Any change in the data selection format which is required requires modification of the special purpose software which is resident in the host computer. It will therefore be appreciated that such terminal emulation and connectivity systems are of only limited value.

In open database connectivity systems it is essential that the host computer database management system must be open database connectivity compliant. Special purpose software is required in the PC and in the host computer, and this must be built using open database connectivity drivers. Additionally, the software must be written in SQL programming language. It will thus be appreciated that significant software skills are required in order to install and operate an open database connectivity system. Similarly, significant software skills are also required in installing and operating a technical emulation and connectivity system.

There is therefore a need for a communication system which facilitates communication between a PC and a host computer wherein the PC operates in a PC compatible environment, and the host computer operates in a non-PC compatible environment, which overcomes the problems of these known systems .

The present invention is directed towards providing such a communication system, and also to providing a PC and a host computer configured with the communication system.

According to the invention there is provided a communication system for facilitating communication between a personal computer and a host computer, wherein the personal computer operates in a PC compatible environment, and the host computer operates in a non-PC compatible environment, the communication system comprising a plurality of objects, namely, a first object which in use resides in the PC for initiating communication from the PC to the host, a second object which in use resides in the PC, the second object interacting with the first object for interpreting requests from the first object for executing a logon to the host procedure, a third object which in use resides in the host 10 computer and controls requests from the PC on the logon to host channel and translates the requests into host executable procedure calls, a fourth object which in use resides in the host computer for receiving host executable instructions from the third object, and for controlling, interpreting and creating host procedures for carrying out the host executable instructions, a fifth object which in use is resident in the host computer, the fifth object interacting with the fourth object for controlling data selection and acquisition procedures created by the fourth object, and for executing the data selection and acquisition procedures, a sixth object which in use is resident in the host computer for relaying data selected and acquired by the fifth object to the PC, and a seventh object which in use is resident in the host computer for controlling the management of the host resident databases for maintaining the integrity of the host resident databases during execution of the host procedures carried out by the fifth object.

In one embodiment of the invention the first object takes possession of a communications port in the PC, and sends a bit-stream to the host computer, and waits for a bit-stream to return from the host computer, the first object testing the returned bit-stream from the host computer for a valid logon bit-stream.

Preferably, on the first object, on determining the return of a valid logon bit-stream from the host computer passes control of the PC to the second object.

Advantageously, the first object releases the communications port of the PC and reports a communication failure status on failing to detect the return of a valid logon bit-stream within a predetermined period of time.

In another embodiment of the invention the second object steps the PC through validation procedure requests from the host computer, and on satisfying the validation procedure requests, the second object executes host environment parameter routines and requests corresponding execution of the routines by the host computer.

Preferably, the second object on determining that the PC is unable to satisfy the validation procedure requests, reports a failure status message.

In another embodiment of the invention the third object translates the PC requests into a host executable procedures prior to passing the PC requests to the fourth object.

Preferably, the third object translates results received from the fourth object in response to a PC request for returning to the PC.

In a further embodiment of the invention the fourth object controls requests to the seventh object.

In a still further embodiment of the invention the fifth object carries out all data selection and acquisition procedures on the host computer for reducing the amount of data sent to the PC in response to a PC request.

In another embodiment of the invention the sixth object interacts with the third object for compressing data to Ί be sent to the PC in response to a PC request for shortening the length of blocks of data to be transmitted.

Preferably, the sixth object compresses the data by 5 eliminating gaps, empty fields, redundancy and/or unnecessary data, and replaces all such gaps, empty fields, redundancy and unnecessary data by one single character plus one predetermined replacement factor character.

In one embodiment of the invention part of the sixth object in use is resident in the PC for reconstructing the compressed data.

Additionally, the invention provides a PC operating in a PC compatible environment, comprising the communication system according to the invention for facilitating communication between the PC and the host computer.

The invention will be more clearly understood from the following description of a preferred embodiment thereof which is given by way of example only with reference to the accompanying drawings, in which; Fig. 1 is a block representation of a communication system for facilitating communication between a PC and a host computer wherein the PC is operating in a PC compatible environment, and the host computer is operating in a non-PC compatible environment, Fig. 2 is a block representation of a PC and a host computer configured with the communication system of Fig. 1, Fig. 3 is a block representation illustrating a plurality of PC's communicating with two host computers configured with the communication system of Fig. 1, Fig. 4 is a flow chart illustrating communication between a PC and host computer operating under the communication system of Fig. 1, Fig. 5 is a flow chart of a typical communication between the PC and the host computer operating under the communication system of Fig. 1, Fig. 6 is a block representation of a PC which communicates with a host computer using the communication system of Fig. 1, and Fig. 7 is a flow chart of a protocol routine for use in the communication system of Fig. 1.

Referring to the drawings there is provided a communication system according to the invention indicated generally by the reference numeral 1 for controlling communication between a PC 2 operating in a PC compatible environment and a host computer 3 operating in any one of a number of non-PC compatible environments, for example, a Digital VAX environment, and in particular, for selecting and accessing data from the host computer 3. The communication system comprises seven objects, each of which are written in C++, which are separate from each other, but which interact with each other as necessary in the execution of requests or queries to the host computer 3 from the PC 2 for selecting and accessing data in the data files of the host computer 3. The communication system is resident in the PC 2 and the host computer 3 as will now be described.

The first of the seven objects, namely, the first object 11 is a connect to host object, and in use is resident in the PC 2. The first object 11 takes possession of a communications port in the PC 2 and sends a bit-stream to the host computer, and then waits for a logon bit-stream to return from the host computer. On receiving the bit-stream returned from the host computer, the first object 11 tests the validity of the returned bit-stream to ascertain if it is a valid logon bit-stream, and on confirming the returned bit-stream as a valid logon bit-stream, the first object passes the bit-stream to the second object 12, which is a logon-to-host object which will be described below. If the returned bit-stream is not a valid logon bit-stream, or if a returned bit-stream is not detected by the first object within a predetermined period of time, typically, a few seconds, the first object releases the communications port and reports a connection failure status signal.

The second object 12, which is the logon-to-host object is resident in the PC 2 and interacts with the first object for interpreting requests from the first object to execute the logon-to-host computer procedure. The second object 2 steps the PC through access validation procedure requests, and on the validation request being satisfied the second object 12 then executes host environment parameter routines, and request execution by the relevant object resident in the host computer 3. Should the second object 12 determine that the PC 2 is unable to satisfy the validation procedure requests with appropriate valid responses, the validation routine of the second object 12 reports the status of the failure to the PC 2.

The third object 13 is a procedure call interface object, and is resident in the host computer 3. The third object 13 controls PC requests from the logon-tohost channel, and in turn passes the requests to a fourth object 14, namely, a host procedure processor object which will be described below. Additionally, the third object 3 passes each request from the logonto-host channel to a sixth object 16, namely, a compression and redundancy object which is also described below. Each request from the PC on the logon-to-host channel also have to be translated into host executable procedure requests prior to execution by the fourth object 14, namely, the host procedure processor object, and the third object 13 carries out the necessary translation of the PC requests so that they are executable in the host computer.

Additionally, the third object 13 translates results received from the fourth object 14 in response to requests from the PC into PC executable instructions. The translated results which are prepared by the third object 13 are then passed to the sixth object 16, namely, the compression and redundancy object in order to reduce the length of data blocks to be transmitted from the host computer 3 to the PC 2 over the logon-tohost channel.

The fourth object 14, which is the host procedure processor object is resident in the host computer 3, and controls the translated requests from the PC 2 received from the third object 13, and executes the PC requests on the host computer. The fourth object 14 interprets the PC requests, and creates host processes to carry out the PC requests received from the third object 13 in host executable instructions.

The fifth object 15 which is a data management object 10 is resident in the host computer 3, and interacts with the seventh object 17 which is described below, and controls data selection and acquisition procedures in the host computer 3. These data selection acquisition procedures are executed on the host computer 3 so that the results in response to requests from the PC 2 are obtained and calculated on the host computer 3, which is a more powerful computer. Additionally, by preparing the results on the host computer 3, the amount of data transmitted to the PC 2 is reduced, and additionally, the amount of data to be compressed by the sixth object 16 is also reduced.

The sixth object 16, namely, the compression and redundancy object is resident in the host computer 3 and compresses and removes redundant data to be transmitted from the host computer 3 to the PC 2. The sixth object 16 interacts with the third object 13, namely, the procedure call interface object from which it processes requests. The data compression and redundancy routines use algorithms which will be well known to those skilled in the art for shortening the length of the data blocks to be transmitted from the host computer 3 to the PC 2. The compression and redundancy routines eliminate gaps, empty fields, redundancy or unnecessary data. For example, the compression and redundancy routines remove recurrent ASCII characters and replace the ASCII characters by inserting one single character, plus one predetermined replacement factor character. This will be well known to those skilled in the art. The sixth object 16 is a particularly important object in user terms, as the results to PC requests which are prepared by the host computer 3 or returned to the PC 2 with optimal response time performance.

The seventh object 17 is a file and record management object, which is resident in the host computer 3 and controls the management of the host computer resident databases. It is essential that files and record structures which constitute the host computer resident databases are maintained so that the integrity of the data is not compromised. The seventh object 17 interacts through dedicated host library routines, which will be known to those skilled in the art with the host operating system during execution. This ensures that the host computer resident databases and the integrity of the host resident databases is maintained. The seventh object 17 operates under the control of the fourth object 14, namely, the host procedure processor.

Turning now to Fig. 2 the PC 2 is illustrated communicating with the host computer 3 through a modem 20. Database files 21 are illustrated in the host computer, and the first and second objects 11 and 12 of the communication systems 1 which are resident in the PC 2 are indicated by the reference numeral 22, while the third to the seventh objects 13 to 17 of the communicating system 1 which are resident in the host computer 3 are illustrated by the reference numeral 23.

Fig. 3 illustrates an alternative arrangement for connecting a plurality of PC's 2 into two host computers 3. For example, one of the host computers 3a may be a computer which deals with administration of a business, while the second host computer 3b may be one which controls the manufacturing operation of a business. Communication between the PC 2 and the host computer 3a is through a terminal server 24. Four of the PC's 2 are illustrated connected together on a local area network, and are connected to the host computers 3a and 3b through an internet backbone 25.

Fig. 4 shows a flow chart which illustrates how communication between the PC 2 and a host computer 3 is controlled by the communication system. In this case, the host computer 3 is a digital, VAX computer. Communication between the PC 2 and the host computer 3 is by way of an RS232C link. Block 100 activates the communication system and is windows executable, and seizes the communications port of the PC 2 at a memory address. Block 100 issues instructions to the UART register addresses of the PC 2 and also sends packets of data to be sent to the host computer 3 for binary translation.

Block 101 controls a UART and voltage potential instruction set which translates a parallel stream of bits to binary, and drives the bits stream to an appropriate voltage for transmission through a RS232C comm's port of the PC 2. Block 102 controls the comm's port and passes the bit stream across a suitable physical transport medium, namely a cable 103 at the . RS232C voltage potential.

Block 104 in the host computer 3 controls the serial VAX port, and causes a VMS listener to monitor all configured devices for interrupts. If an interrupt is detected, the VMS either creates a process table entry or executes a loginout command. Block 105 which creates the process table entry creates an environment to execute access/user commands or user programmes. Block 106 which executes the loginout function accesses success/validation against UAF parameters and passes control to a command line interpreter of the host computer 3. Block 107 controls the command line interpreter, and at this stage DCL commands are interpretable, and the command line interpreter is available to execute DCL instructions from the PC 2.

Block 108 controls the execution of the server programme and a command line interpreter accepts DCL commands from the PC 2 to execute server process routines in the host computer 3.

In order to secure the transfer of packets of data, the communication system 1 takes control of the central processing unit and the UART of the PC 2 for the duration of the transfer of each packet of data. The protocol of the communication system uses C++ encoded objects which are encapsulated in the PC 2 executable which is compiled to produce Microsoft Windows DLL using Microsoft Windows software developer kit methodology. The executable in the host computer 3 is also written in C++, and is compiled against the operating systems libraries which are appropriate to the hardware platform of the host computer 3. The communications system comprises a series of objects which are compiled as a single executable, and this executable is called up from a windows icon and loaded in the memory of the PC 2. The size of the data packets is determined depending on the type of central processing unit of the PC 2, the bus speed or on the speed of the communications link between the PC 2 and the host computer 3. As will be described below the PC 2 provides a vast array of options which may be selected prior to initiating communications between the PC 2 and the host computer 3. A new query may be built in the PC 2 prior to communication between the PC 2 and the host computer 3. A previously built query may be selected, and may be transmitted in it's original form or modified.

Fig.5 illustrates a flow chart of a typical communication between the PC 2 and the host computer 3. The commands and processing which is carried out by the PC 2 are illustrated by the blocks to the right hand side of the chain dotted line 110, while those carried out by the host computer 3 are illustrated by the blocks to the left hand side of the broken line 110.

Block 111 starts the communication system routine in the PC 2. Block 112 permits the user of the PC 2 to define the query which is to be communicated to the host computer 3. This as discussed above may be a new query, an existing query or a modified existing query.

Block 113 executes the host logon command. The communication system routine remains at block 113 until logon has been successfully established. During establishment of logon with the host computer 3 block 113 communicates with block 114 of the host computer 3, which establishes connection between the host computer 3 and the PC 2. On communication being successfully established between the PC 2 and the host computer 3, the communications system routine moves to block 115 which commences execution of the query. At this stage the PC 2 and the host computer 3 are in direct communication.

Block 115 invokes the server executable block 116 which in turn causes the host computer 3 to execute the server process and set parameter environment and other necessary house keeping functions. Block 118 in the PC 2 awaits a server alive acknowledgment which is communicated from block 119 of the host computer 3. After transmitting the server alive acknowledgment the routine in the host computer 3 moves to block 120 and awaits the query. In the meantime after receiving the alive acknowledgement block 121 in the PC 2 examines the query definition, and moves to block 122 which checks if compression would be advantageous. If not, a packet of uncompressed data of the query is sent by block 123, and if compression would be advantageous, the routine moves to block 124, which compresses the data and sends the data packet of the query to block 120. Block 120, if the data is compressed decompresses the packet of data and builds the query, or otherwise builds the query from the data packets received from block 123. Block 125 in the PC 2 awaits an acknowledgment from the host computer 3 which is sent by block 126 after the data packet has been received by block 120. Block 127 in the PC 2 checks if all the packets of data constituting the query have been sent to the host computer 3, and if not the PC 2 is returned to block 121.

On block 127 determining that all the packets of data constituting the query have been sent to the host computer 3, block 127 transmits a signal to block 128 in the host computer 3 which causes the host computer 3 to execute the query. Block 129 in the PC 2 awaits the result from the host computer 3, and when block 128 has completed execution of the query the result is passed through block 130 which sends the result in data packets to block 133 of the PC 2, which displays the result on the visual display of the PC 2. Block 130 if appropriate compresses the data prior to returning the data in packets to block 133. Block 131 of the PC 2 sends an acknowledgment to the host computer 3 on block 133 successfully receiving the result data packet. The acknowledgment is received by block 132 of the host computer 3, and the host computer 3 remains in a loop between blocks 129, 130 and 132 until the final data packet of the result has been received by block 133 and an acknowledgment has been received from block 131 by block 132.

Block 133 returns control of the PC 2 to block 115.

This gives the user an opportunity to amend or modifying the query which is permitted by block 135.

After the query has been amended or modified the PC 2 moves to block 136 which checks if the amended of modified query is to be run again, and if so the PC 2 returns to block 115, which causes the query to be executed by the host computer 3 as already described.

Otherwise, the PC 2 moves to block 137 which provides for saving of the query format if desired. Block 138 ends the communication routine in the PC 2, and block 139 ends the communication routine in the host computer 3.

As discussed above it is essential that control be taken of the central processing unit and of the UART of the PC 2 for the duration of the transfer of a packet of data. Fig. 6 shows a schematic layout of the PC 2. The central processing unit is indicated by the reference numeral 150. The UART is indicated by the reference numeral 151. Serial transmit and receive ports are indicated by the reference numerals 152 and 153, respectively. Memory locations are indicated by the reference numeral 154 and dynamic memory addresses are located by the reference numeral 155.

Fig. 7 shows a flow chart of the protocol routine for disabling interrupts from the central processing unit to the UART. The protocol routine opens the UART registers at the memory address assigned by the basic input output system, and the central processing unit 150 is held in a tight loop by the protocol routine examining the first in first out transmit register of the UART until a release condition is detected, and the central processing unit is released. The duration of the tight loop function is held for one character length or until the end of a packet of data is detected, and a release instruction is issued by the protocol routine. The protocol routine disables the central processing interrupts from the UART by changing the status of the UART IER register. The central processing unit is tight looped and polling and listening for an appropriate bit to be sent to the UART transmit holding register. The character is cleared and moved to a buffer defined by the host computer 3, and this condition is held for the duration of a single byte transmission. The central processing unit 150 is released and the counter is implemented. The routine continues until the end of a packet of data is detected or implemented.

The invention is not limited to the embodiment hereinbefore described which may be varied in construction and detail.

Claims

1. A communication system for facilitating communication between a personal computer and a host computer, wherein the personal computer operates in a PC compatible environment, and the host computer operates in a non-PC compatible environment, the communication system comprising a plurality of objects, namely, a first object which in use resides in the PC for initiating communication from the PC to the host, a second object which in use resides in the PC, the second object interacting with the first object for interpreting requests from the first object for executing a logon to the host procedure, a third object which in use resides in the host computer and controls requests from the PC on the logon to host channel and translates the requests into host executable procedure calls, a fourth object which in use resides in the host computer for receiving host executable instructions from the third object, and for controlling, interpreting and creating host procedures for carrying out the host executable instructions, a fifth object which in use is resident in the host computer, the fifth object interacting with the fourth object for controlling data selection and acquisition procedures created by the fourth object, and for executing the data selection and acquisition procedures, a sixth object which in use is resident in the host computer for relaying data selected and acquired 5 by the fifth object to the PC, and a seventh object which in use is resident in the host computer for controlling the management of the host resident databases for maintaining the integrity of the host resident databases during execution of the 10 host procedures carried out by the fifth object.

2. A communication system as claimed in Claim 1 in which the first object takes possession of a communications port in the PC, and sends a bit-stream to the host computer, and waits for a bit-stream to 15 return from the host computer, the first object testing the returned bit-stream from the host computer for a valid logon bit-stream.

3. A communicating system substantially as described herein with reference to and as illustrated in the 20 accompanying drawings.

4. A PC operating in a PC compatible environment, and a host computer operating in a non-PC compatible environment, comprising the communication system as claimed in any preceding claim for facilitating communication between the PC and the host computer.

5. A PC and a host computer configured with the communication system substantially as described herein 5 with reference to and as illustrated in the accompanying drawings.