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Tutorial 6 - Network Programming
 

In this tutorial, network programming is explained using a simple client server example. We use windows sockets for client-server communication. 


What is a Socket ?


A socket is a communication endpoint — an object through which a Windows Sockets application sends or receives packets of data across a network. A socket has a type and is associated with a running process and it may have a name. Currently, sockets generally exchange data only with other sockets in the same "communication domain," which uses the Internet Protocol Suite.


Two socket types are available:

  • Stream sockets

        Stream sockets provide a data flow without record boundaries: a stream of bytes. Streams are guaranteed to be delivered and to be correctly sequenced and unduplicated.


  • Datagram sockets

        Datagram sockets support a record-oriented data flow that is not guaranteed to be delivered and may not be sequenced as sent or unduplicated. "Sequenced" means that packets are delivered in the order sent. "Unduplicated" means that you get a particular packet only once. 


    Both kinds of sockets are bidirectional; ie data can be communicated in both directions simultaneously (full-duplex).


    Namespaces used 


    System.Net- The System.Net namespace provides a simple programming interface for many of the protocols used on networks.


    Some of the classes in this namespace:


    IPAddress

    Provides an Internet Protocol (IP) address.

    SocketAddress

    Stores serialized information from EndPoint derived classes.


        System.Net.Sockets- The System.Net.Sockets namespace provides a managed implementation of the Windows Sockets (Winsock) interface for developers who need to tightly control access to the network.


    Some of the classes in this namespace:


    NetworkStream

    Provides the underlying stream of data for network access.

    Socket

    Implements the Berkeley sockets interface.

    SocketException

    The exception that is thrown when a socket error occurs.

    TcpClient

    Provides client connections for TCP network services.

    TcpListener

    Listens for connections from TCP network clients.


       


              Setting Up Communication Between a Server and a Client        


      Server Client

      //Store the IP Address  

      Dim ipAddress As IPAddress = ipAddress.Parse("127.0.0.1") 

       
      //Initializes the Listener

      Dim tcpListener As New

      TcpListener(ipAddress, 8000)

       
      // start listening

      tcpListener.Start() 

       
        //create new client and connect to the sesrver

      Dim tcpClient As New TcpClient 
      tcpClient.Connect("127.0.0.1", 8000)

      //Accept the connection

      Dim soc As Socket = tcpListener.AcceptSocket()

       
      //Get the data

      Dim byteData(100) As Byte
      Dim size As Integer = soc.Receive(byteData)

      //reads the stream

      Dim stm As Stream = tcpClient.GetStream() 

      //sending the data

      stm.Write(byteData, 0, byteData.Length()) 

      /* clean up */

      soc.Close()
      tcpListener.Stop()

      //closing the client connection

      tcpClient.Close()


       Click on the appropriate  link below to see the video and the source.



    • Download Server Example Source

      Download Client Source Example

         





       
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