sockets - Berkeley Socket Examples

Description

This archive contains C source code sample implementations of clients and servers using Berkeley Socket. Most of the source code evolved from code that I originally wrote back in 1990. Every few years I was using it as a reference and updating it to replace obsolete functions with modern functions. I've placed the resulting code on github so that I could find it and access it from just about anywhere.

These files are released under the BSD License.

More information on Berkeley sockets and this echo server implementation may be found at: https://michaeldipperstein.github.io/sockets.html

Files

File Name	Contents
echoclient.c	TCP/IP echo client example using getaddrinfo() to find the server address
echoserver.c	TCP/IP echo server example with poll() loop
echoclient_udp.c	UDP/IP echo client example using getaddrinfo() to find the server address
echoserver_udp.c	UDP/IP echo server example
Makefile	makefile for this project (assumes gcc compiler and GNU make)
README.MD	This file

Building

To build these files with GNU make and gcc:

1. Open a terminal
2. Change directory to the directory containing this archive
3. Enter the command "make" from the command line.

Usage

NOTE: It is not possible to mix and match TCP and UDP client/server pairs.

echoserver or echoserver_udp

echoserver <port number>

echoserver_udp <port number>

The echoserver will not exit until CTRL-c is pressed.

echoclient or echoclient_udp

echoclient <server hostname or address> <port number>

echoclient_udp <server hostname or address> <port number>

Hit Enter on a blank line to exit from an echoclient.

Multiple echoclients may connect to a single echoserver instance.

History

12/27/17

• Initial release

12/30/17

• Added UDP client and server examples

08/08/20

• Added polling and signal handling to allow UDP examples to exit cleanly when waiting to receive data

08/18/20

• Rewrote TCP code so that the echoserver will echo a message will be echoed to every connected echoclient.
• TCP echoserver now actively tracks all connected echoclient sockets.
• Replaced select() loop with poll() loop in TCP code.

08/30/20

• Rewrote UDP code so that the echoserver will echo a message will be echoed to every connected echoclient.
• UDP echoserver now actively tracks all echoclient socket addresses.
  • Address is obtained when client sends its first message.
  • Address is released when the client sends and empty message.
• Replaced select() loop with poll() loop in USP code.

TODO

• Send and receive messages of any size
• Apply timeout to client connect attempts
• Add support for IPv6

BUGS

• No known bugs

AUTHOR

Michael Dipperstein (mdipperstein@gmail.com)