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A sample libevent-based network socket server that presents a simple command line interface to multiple connecting clients.

branch: master
README.mkd

cliserver

A libevent-based server that handles simple commands from multiple clients. Created while learning to use libevent, this is intended to help alleviate the relative dearth of libevent sample code. See the reasonably-well-commented source code for additional information, and feel free to borrow the macros at the beginning of cliserver.c (though if you think they're useful, credit would be appreciated).

This code has been tested not to leak memory or file descriptors under a variety of conditions using valgrind.

Note that evbuffer_readline() is a potential source of denial of service, as it does an O(n) scan for a newline character each time it is called. One solution would be checking the length of the buffer and dropping the connection if the buffer exceeds some limit (dropping the data is less desirable, as the client is clearly not speaking our protocol anyway). Another (more ideal) solution would be starting the newline search at the end of the existing buffer. The server won't crash with really long lines within the limits of system RAM (tested using lines up to 1GB in length), it just runs slowly.

Clients connect to the server on port 14310, allowing them to run the following commands:

  • echo: Print the command line.
  • help: Print a list of commands and their descriptions.
  • info: Print connection information.
  • quit: Disconnect from the server.
  • kill: Shut down the server.

A sample client interaction:

> help
echo:   Prints the command line.
help:   Prints a list of commands and their descriptions.
info:   Prints connection information.
quit:   Disconnects from the server.
kill:   Shuts down the server.
> info
Client address: ::1
Client port: 60642
> echo This is just a simple test program.
This is just a simple test program.
> quit

Compiling cliserver

Compile the server with make, run it with ./cliserver. Connect to the server using netcat: nc localhost 14310.

You will need libevent 1.x (I'm using 1.4.13 from Ubuntu 10.10), gcc, and GNU make to compile this code. It should, in theory, be easily portable to libevent 2.x.

Copyright

(C)2010 Mike Bourgeous, licensed under 2-clause BSD

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