Building a simple server client application using C#

Hello everybody! Here I am again to show you a simple, or maybe I can say the simplest way to build a server client application using C#. I said last time I would write a Rails code, but, promise to do that next time.

It’s just a bunch of lines and there you go, you already have your application running, you can test both (server and client) on your computer, or if you have another one, you can test and play with it too.

After the tutorial, I’ll let the whole code for you to download. But before that I will go through it step by step, trying to make things clear.

So, stop the chit chat and let’s get some work done!

First I’m going to explain the server code, and when it’s already running we jump into our client, which in this case I’ll consider only one, but nothing prohibits you to connect more than one client to you server.

By the way, I’m using Visual Studio 2010 and Windows 7.

Step 1: Create your C# application.

Step 2: You will need those LOC at the top.

1 using System;
2 using System.Text;
3 using System.Net;
4 using System.Net.Sockets;

Step 3: Everything must be inside a “try… catch…” block. So, you now create an IPAdress using your own IP, a TcpListener which will get your clients and then start it.

1 IPAddress ipAdress = IPAddress.Parse("172.21.5.99"); 
2 // You can use local IP as far as you use the 
3 //same in client
4 
5 // Initializes the Listener
6 TcpListener myList = new TcpListener(ipAdress,8000);
7 
8 // Start Listeneting at the specified port
9 myList.Start();

Step 4: Showing a message to the user is important, so:

1 Console.WriteLine("Server running - Port: 8000");    
2 Console.WriteLine("Local end point:" + 
3                             myList.LocalEndpoint );
4 Console.WriteLine("Waiting for connections...");

Step 5: Now that your list is already running, you’re waiting for a connection, when it does, you must treat it creating a socket that will get the client.

 1 Socket s = myList.AcceptSocket();
 2 // When accepted
 3 Console.WriteLine("Connection accepted from "
 4                         + s.RemoteEndPoint);
 5 
 6 byte[] b = new byte[100];
 7 int k = s.Receive(b);
 8 Console.WriteLine("Recieved...");
 9 
10 for (int i=0;i<k;i++)
11 {
12     Console.Write(Convert.ToChar(b[i]));
13 }

Step 6: Besides sending a message to the user that the server is already running, it’s also important to send an automatic message back to the client, so it does know that the connection was succeeded.

1 ASCIIEncoding asen = new ASCIIEncoding();
2 s.Send(asen.GetBytes("Automatic message: 
3                 + "String received by server!"));
4 Console.WriteLine("\n Automatic message sent!");

Step 7: Finally close the socket and stop the list.

1 s.Close();
2 myList.Stop();

Step 8: You can treat the “catch” the way you prefer, I just went for throwing a message.

1 Console.WriteLine("Error..... " + e.StackTrace);

Well, since we have now our server running perfectly, let’s build the client.

Step 1: Similar to your server, the client will need:

1 using System;
2 using System.IO;
3 using System.Net;
4 using System.Text;
5 using System.Net.Sockets;

Step 2: Alright, do not forget to build your code inside a “try… catch…”, you will need now a TcpClient and a Stream, so follow the code below:

 1 TcpClient tcpclnt = new TcpClient();
 2 Console.WriteLine("Connecting.....");
 3 
 4 tcpclnt.Connect("172.21.5.99",8001); 
 5 // Use the ipaddress as in the server program
 6 
 7 Console.WriteLine("Connected...");
 8 Console.Write("Enter the string to be sent: ");
 9 
10 String str = Console.ReadLine();
11 Stream stm = tcpclnt.GetStream();

Step 3: Remember that when we got the message from our client we converted from ASCII, so to send a message we sure must convert to it.

 1 ASCIIEncoding asen = new ASCIIEncoding();
 2 byte[] ba = asen.GetBytes(str);
 3 Console.WriteLine("Sending...");
 4 
 5 stm.Write(ba,0,ba.Length);
 6 
 7 byte[] bb = new byte[100];
 8 int k = stm.Read(bb,0,100);
 9 
10 for (int i = 0;i < k; i++)
11 {
12 Console.Write(Convert.ToChar(bb[i]));
13 }

Step 4: Finally, close your TcpClient:

1 tcpclnt.Close();

Step 5: And the “catch” block:

1 Console.WriteLine("Ops! Error! " + e.StackTrace);

Voila! You now have a simple server client application. Note that it’s just a connection and messages send, you can play with your code, finding out new features and adapting it to your need.

Hope you have enjoyed!

Thanks for all the attention.