Using a Synchronous Server Socket

Synchronous server sockets suspend the execution of the application until a connection request is received on the socket. Synchronous server sockets are not suitable for applications that make heavy use of the network in their operation, but they can be suitable for simple network applications.

After a Socket is set to listen on an endpoint using the Bind and Listen methods, it is ready to accept incoming connection requests using the Accept method. The application is suspended until a connection request is received when the Accept method is called.

When a connection request is received, Accept returns a new Socket instance that is associated with the connecting client. The following example reads data from the client, displays it on the console, and echoes the data back to the client. The Socket does not specify any messaging protocol, so the string "<EOF>" marks the end of the message data. It assumes that a Socket named listener has been initialized and bound to an endpoint.

Console.WriteLine("Waiting for a connection...")
Dim handler As Socket = listener.Accept()
Dim data As String = Nothing
            
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
            
Console.WriteLine("Text received : {0}", data)

Dim msg As Byte() = Encoding.ASCII.GetBytes(data)
handler.Send(msg)
handler.Shutdown(SocketShutdown.Both)
handler.Close()

Console.WriteLine("Waiting for a connection...");
Socket handler = listener.Accept();
String data = null;

while (true) {
    bytes = new byte[1024];
    int bytesRec = handler.Receive(bytes);
    data += Encoding.ASCII.GetString(bytes,0,bytesRec);
    if (data.IndexOf("<EOF>") > -1) {
        break;
    }
}

Console.WriteLine( "Text received : {0}", data);

byte[] msg = Encoding.ASCII.GetBytes(data);
handler.Send(msg);
handler.Shutdown(SocketShutdown.Both);
handler.Close();

See Also

Concepts

Using an Asynchronous Server Socket
Synchronous Server Socket Example
Listening with Sockets