6.Network Programming

In this tutorial, network programming is explained using a simple client server example. For connecting between the client and the server we use windows sockets.


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:


    Provides an Internet Protocol (IP) address.


    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:


    Provides the underlying stream of data for network access.


    Implements the Berkeley sockets interface.


    The exception that is thrown when a socket error occurs.


    Provides client connections for TCP network services.


    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("") 

//Initializes the Listener

Dim tcpListener As New

TcpListener(ipAddress, 8000)

// start listening


  //create new client and connect to the sesrver

Dim tcpClient As New TcpClient 
tcpClient.Connect("", 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 */


//closing the client connection


Network Programming using VB.NET



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