In this section we will discuss how to implement a simple
client-server application using Sockets in C#. There will be two distinct
applications, i.e., a Server application and a Client application. The Server
application will connect to a port and be in the listen mode waiting for a
Client to connect. Once the Client is connected, it will send a test message to
the Server application using a StreamWriter. This text message will then be
displayed in the Server application's console.
Here is the source code of the Server application.
Listing 3: The SocketServer class
using System;
using System.Text;
using System.Net;
using System.Net.Sockets;
class SocketServer
{
public static void Main()
{
StreamWriter streamWriter;
StreamReader streamReader;
NetworkStream networkStream;
TcpListener tcpListener = new TcpListener(5555);
tcpListener.Start();
Console.WriteLine("The Server has started on port 5555");
Socket serverSocket = tcpListener.AcceptSocket();
try
{
if (serverSocket.Connected)
{
while (true)
{
Console.WriteLine("Client connected");
networkStream = new NetworkStream(serverSocket);
streamWriter = new StreamWriter(networkStream);
streamReader = new StreamReader(networkStream);
Console.WriteLine(streamReader.ReadLine());
}
}
if (serverSocket.Connected)
serverSocket.Close();
Console.Read();
}
catch (SocketException ex)
{
Console.WriteLine(ex);
}
}
}Refer to the code snippet given above. The Server
application starts the port 5555; displays a relevant message and waits for the
incoming requests from the Client to connect to it. Now, when you run this
application, the message "The Server has started on port 5555" will
be displayed on the Server application's console. As soon as a Client gets
connected to the same port, the message "Client connected" is
displayed on the console. Here is the output when you execute this application.
Figure 4: The SocketServer console when started
Next, we will take a look at the source code of the Client
application that will connect to the Server application using the same port,
i.e., 5555. Here is the code.
Listing 4: The SocketClient class
using System;
using System.Text;
using System.Net;
using System.Net.Sockets;
class SocketClient
{
static void Main(string[]args)
{
TcpClient tcpClient;
NetworkStream networkStream;
StreamReader streamReader;
StreamWriter streamWriter;
try
{
tcpClient = new TcpClient("localhost", 5555);
networkStream = tcpClient.GetStream();
streamReader = new StreamReader(networkStream);
streamWriter = new StreamWriter(networkStream);
streamWriter.WriteLine("Message from the Client...");
streamWriter.Flush();
}
catch (SocketException ex)
{
Console.WriteLine(ex);
}
Console.Read();
}
}When you execute the Client application, here is how the
output will look like at the Server application’s console.
Figure 5: The SocketServer console when the client
is connected
Note that the message "Client connected" and the
text sent by the client, "Message from the Client…", is displayed at
the Server application’s console.
