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This short chapter descripes client server communication as it
relates to zWebit and the interface communications programs in
general.
In addition to other protocols, zWebit interface programs utilize the industry standard TCP/IP Communications client/server model. Interface programs that can receive data are typically server programs. Interface programs that send data are typically client programs. Server programs must be active before a client program can connect to it and send data.
There are many excellent books which delve into the intracacies of network programming, TCP/IP, and socket communications (recommendation: Unix systems Programming for SVR4 by David A. Curry). It is beyond the scope of this work to fully describe networking concepts.
The following table identifies the order of function calls used by client/server programs. In general, communication between a server program and a client program is performed in the following order.
| Description | Server Function Call | Client Function Call |
|---|---|---|
| Create a socket | socket ( ) | socket ( ) |
| Bind socket to address | bind ( ) | |
| Listen for connection | listen ( ) | |
| Connect to server | connect ( ) | |
| Accept connection | accept ( ) | |
| Process loop | ||
| *Send data | send ( ) | |
| *Receive data | recv ( ) | |
| *Send ACK | send ( ) | |
| *Receive ACK | recv ( ) | |
| Close connection | close ( ) | |
| Close socket | close ( ) | close ( ) |
* Note receive data, send data, send ACK and receive ACK are all subsidiary processes of the "Process loop."
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Last updated: 07/21/2003