Synchronous Server Socket Example


The following example program creates a server that receives connection requests from clients. The server is built with a synchronous socket, so execution of the server application is suspended while it waits for a connection from a client. The application receives a string from the client, displays the string on the console, and then echoes the string back to the client. The string from the client must contain the string "<EOF>" to signal the end of the message.

Imports System  
Imports System.Net  
Imports System.Net.Sockets  
Imports System.Text  
Imports Microsoft.VisualBasic  
Public Class SynchronousSocketListener  
    ' Incoming data from the client.  
    Public Shared data As String = Nothing  
    Public Shared Sub Main()  
        ' Data buffer for incoming data.  
        Dim bytes() As Byte = New [Byte](1024) {}  
        ' Establish the local endpoint for the socket.  
        ' Dns.GetHostName returns the name of the   
        ' host running the application.  
        Dim ipHostInfo As IPHostEntry = Dns.Resolve(Dns.GetHostName())  
        Dim ipAddress As IPAddress = ipHostInfo.AddressList(0)  
        Dim localEndPoint As New IPEndPoint(ipAddress, 11000)  
        ' Create a TCP/IP socket.  
        Dim listener As New Socket(AddressFamily.InterNetwork, _  
            SocketType.Stream, ProtocolType.Tcp)  
        ' Bind the socket to the local endpoint and   
        ' listen for incoming connections.  
        ' Start listening for connections.  
        While True  
            Console.WriteLine("Waiting for a connection...")  
            ' Program is suspended while waiting for an incoming connection.  
            Dim handler As Socket = listener.Accept()  
            data = Nothing  
            ' An incoming connection needs to be processed.  
            While True  
                bytes = New Byte(1024) {}  
                Dim bytesRec As Integer = handler.Receive(bytes)  
                data += Encoding.ASCII.GetString(bytes, 0, bytesRec)  
                If data.IndexOf("<EOF>") > -1 Then  
                    Exit While  
                End If  
            End While  
            ' Show the data on the console.  
            Console.WriteLine("Text received : {0}", data)  
            ' Echo the data back to the client.  
            Dim msg As Byte() = Encoding.ASCII.GetBytes(data)  
        End While  
    End Sub  
End Class 'SynchronousSocketListener  

Synchronous Client Socket Example
Using a Synchronous Server Socket
Socket Code Examples