VB.NET Technology

A Socket is an End-Point for communication link between two programs (Server Program and Client Program ) running on the same network .Socket is bidirectional. We have to write two programs for implementing a socket application in VB.Net.

 Server Socket Program ( Server )
  Client Socket Program ( Client ) .

In VB.Net network programming can be done by using namespaces like System.Net and System.Net.Sockets . The classes and methods of these namespaces can communicate across the network. The communication can be either connection oriented or connectionless. They can also be either stream oriented or data-gram based.

Server Socket Program

Server program running on a computer has a socket that bound to a Port Number on the same computer and listening to the client's incoming requests.

Client Socket Program

Client program have to know the IP Address ( Hostname ) of the computer that the VB.Net Server Socket Program resides and the Port Number assign for listening for client's request .

Code for Server Socket Program

Module Module1
    Sub Main()
        Dim serverSocket As New TcpListener(8888)
        Dim requestCount As Integer = 0
        Dim clientSocket As TcpClient = Nothing
        serverSocket.Start()
        Console.WriteLine(" >> Server Started")
        clientSocket = serverSocket.AcceptTcpClient()
        Console.WriteLine(" >> Accept connection from client")
        requestCount = 0
        While (True)
            Try
                requestCount = requestCount + 1
                Dim networkStream As NetworkStream = clientSocket.GetStream()
                Dim bytesFrom As Byte() = New Byte(10024) {}
                networkStream.Read(bytesFrom, 0, CInt(clientSocket.ReceiveBufferSize))
                Dim dataFromClient As String = System.Text.Encoding.ASCII.GetString(bytesFrom)
                dataFromClient = dataFromClient.Substring(0, dataFromClient.IndexOf("$"))
                Console.WriteLine(" >> Data from client - " & dataFromClient)
                Dim serverResponse As String = "Server response " & Convert.ToString(requestCount)
                Dim sendBytes As [Byte]() = Encoding.ASCII.GetBytes(serverResponse)
                networkStream.Write(sendBytes, 0, sendBytes.Length)
                networkStream.Flush()
                Console.WriteLine(" >> " & serverResponse)
            Catch ex As Exception
                Console.WriteLine(ex.ToString())
            End Try
        End While
        clientSocket.Close()
        serverSocket.[Stop]()
        Console.WriteLine(" >> exit")
        Console.ReadLine()
    End Sub
End Module

Code for Client Socket Program

For creating Client design a Client using windows application. Server is console application but client is windows application. Server will give response when client request to sending data or connecting with server.

Namespace New_Client
	Public Partial Class Form1
		Inherits Form
		Private clientSocket As New System.Net.Sockets.TcpClient()
		Public Sub New()
			InitializeComponent()
		End Sub
		Private Sub Form1_Load(sender As Object, e As EventArgs)
			msg("Client Started")
			clientSocket.Connect("127.0.0.1", 8888)
		End Sub
		Public Sub msg(mesg As String)
			textBox1.Text = textBox1.Text + Environment.NewLine + " >> " & mesg
		End Sub
		Private Sub button1_Click(sender As Object, e As EventArgs)
			Dim serverStream As NetworkStream = clientSocket.GetStream()
			Dim outStream As Byte() = System.Text.Encoding.ASCII
			.GetBytes("Message from Client$")
			serverStream.Write(outStream, 0, outStream.Length)
			serverStream.Flush()
			Dim inStream As Byte() = New Byte(10024) {}
			serverStream.Read(inStream, 0, CInt(clientSocket.ReceiveBufferSize))
			Dim returndata As String = System.Text.Encoding.ASCII.GetString(inStream)
			msg("Data from Server : " & returndata)
		End Sub
	End Class
End Namespace