This is a mirror of official site:

Simple Instant Messenger with SSL Encryption in C#

| Monday, July 30, 2012
Inline image 1


Did you ever want to write your own instant messenger program like Skype? OK, not so advanced... I will try to explain how to write a simple instant messenger (IM) in C#.NET.

First, some theory. Our instant messenger will work on a client-server model.

Inline image 2

Users have client programs which connect to the server application. Client programs know the server's IP or hostname (e.g.,

The most popular internet protocols are TCP and UDP. We will use TCP/IP, because it is reliable and it has established connection. .NET offers TcpClient and TcpListener classes for this protocol. TCP/IP doesn't offer encryption. It is possible to create own encryption protocol over TCP, but I recommend using SSL (used in HTTPS). It authenticates server (and optionally client) and encrypts connection.

SSL is using X.509 certificates for authenticating. You can buy real SSL certificate (trusted) or generate self-signed certificate (untrusted). Untrusted certificates allow encryption, but authentication isn't safe. We can use them for testing. I made batch script, which generates self-signed certificate in PFX package. My script requires OpenSSL installed in system. I included also one in server application project.

At the end there is your higher-level protocol, which sends messages to specified users and does other IM stuff. I will explain my protocol during article.

You can debug your server and client on the same computer: hostname of server will be localhost or (local IP - same computer).


You should know something about SSL protocol, certificates, and networking.


Create two projects: server and client. Server will be a console application, client - Windows Forms (or WPF). You will need to debug two projects at once, so don't place them in one solution.

Read more: Codeproject
QR: Inline image 3

Posted via email from Jasper-net


Anonymous said...

This is the perfect site for anyone who wants to understand this
topic. You know so much its almost hard to argue with you (not that I
really will need to…HaHa). You definitely put a fresh spin on a topic which has been written about for ages.
Great stuff, just excellent!
Here is my site ... Credit Repair Reviews

Anonymous said...

Excellent site. Plenty of helpful info here. I am sending it
to some friends ans also sharing in delicious.
And of course, thanks to your effort!

Here is my webpage - expert appliance repair Tampa Florida area

Anonymous said...

Hi there mates, fastidious piece of writing and fastidious arguments commented at this place, I am
genuinely enjoying by these.

Take a look at my site - yellow pages ad for appliance repair Clearwater FL

Anonymous said...

It's actually a nice and useful piece of information. I am happy that you simply shared this helpful information with us. Please stay us informed like this. Thank you for sharing.

Take a look at my webpage: expert appliance repair Safety Harbor area FL