Chat Program using Asynchronous Socket


Environment: C#

This is a simple chat program using asynchronous socket. This program is act like a client or a server. It can connect to another other PC (installed with the same program) or it can wait for another PC to connect to it.

You can test the program on the same PC by running two instances of the
program. Each one listens to a port (e.g. first is listen to 998 and the second to 999). Click the listen button of both programs, key in the hostname/Host IP Address as “local” or “”, fill in the port number as 999 on the first program (because you want to connect to the second program which listens to port 999),and finally click connect. The IP address will display in the list of the second instance of the program (if successfully connected). At this point, you can start sending messages.

In this simple program, I also demonstrated how the event is raised during
connection, disconnection, sending, and receiving (like the OnConnect, OnSend… in MSVC++ MFC’s socket class).

Update on 17 Apr 2001

This is an update to the
previous code post on 03/22/2002. In the update, I
include the sending and receiving function. The sending and receiving file
is based on my own command that can modify according to u requirement. The
concept is descript as below:







Send Filename and size to

Accepted the file




_ Send signal back, tell client
to start sending



Once signal is received, start
sending file data. (Block by block until end of file)

Store to




_ Successfully received



Actually, you can base on this kind of command to do a lot of stuff like searching file remotely, check remote PC information and other you can think of. Have fun.


Download demo project – 13 Kb

Download source – 10 Kb

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