Socket programming using java

Socket programming using java

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  SOCKET PROGRAMMING INJAVA Narendran Thangarajan, @naren_live, II Year, BE, CSE, SSN College of Engg, Chennai.
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  What started itall..  Internet has emerged as a global ubiquitous media for communication  It has changed the way we live, learn, enjoy, communicate, interact, engage, etc.  To take advantage of this, businesses are ceaselessly trying to offer their services through the internet.  So a huge demand for software developers good in creating internet-enabled applications.
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  Client Server Applications The Web Service is provided by the server and the clients use these services Client Server Network Client machine Server machine A client, where sockets and network This is A server, come in !!
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  Sockets  Introduced inBSD 4.1 UNIX 1981.  Sockets are the endpoints of any communication over the internet.  Sockets are identified by socket addresses.  Socket Address = IP Address + Port Number
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  Why IP Address+ Port number? • IP Address is of the form 10.0.0.1 • Port Number can be anything from 0 to 65,535.
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  Destination Socket =10.0.0.2 : 80 IP Address – Choose network 20.0.0.0 10.0.0.0 30.0.0.0 40.0.0.0
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  Destination Socket =10.0.0.2 : 80 IP Address -> MAC Address – Locate the specific system 10.0.0.1 10.0.0.2
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  Port Number –Process specific Port 10000 Port 11000 Port 120000
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  Understanding Ports OutLook AVG Gmail YM Express Update Port 1 Port 2 Port 3 Port 4 Transport Layer Packet Port num data Network layer
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   Thus virtually,sockets are a connection between the two processes in different systems.  Eg : Let the socket pairs be  10.0.0.1 : 80 and 20.0.0.1 : 2000  192.168.21.10 : 3000 and 192.168.100.1 : 6000
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  Networking Basics –the larger picture  Applications Layer  Standard apps  HTTP TCP STACK  FTP  Telnet Application  User apps (http,ftp,telnet,…)  Transport Layer Transport  TCP (TCP, UDP,..)  UDP Network  Network Layer (IP,..)  IP  Link Layer Link (device driver,..)  Device drivers
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  Network Basics -Where are these sockets?  Applications Layer  Standard apps  HTTP TCP STACK  FTP  Telnet Application  User apps (http,ftp,telnet,…)  Programming Interface: Sockets  SOCKETS Transport  Transport Layer (TCP, UDP,..)  TCP  UDP Network (IP,..)  Network Layer Link  IP  Link Layer (device driver,..)  Device drivers
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  Now into Socket programming..
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  Socket Programming withTCP  Server starts first..  Server Process must be running first  Server must have created a socket which welcomes client’s connection. (Welcoming socket)  Client contacts server by..  Creating Client local TCP socket  Specify IP Address and port number of server process.  When Client socket is created, the connection is established.  When connection is established, server creates a new socket (Connection Socket) to communicate with that client and the Welcoming socket is once again waiting for connections for other clients.
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  Client/Server Socket Interactionin TCP Server create socket, port=x, for incoming request: welcomeSocket = ServerSocket() Client wait for incoming TCP create socket, connection request connection setup connect to hostid, port=x connectionSocket = clientSocket = welcomeSocket.accept() Socket() send request using read request from clientSocket connectionSocket write reply to connectionSocket read reply from connectionSocket close connectionSocket close clientSocket
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  Step 1 : Connection request port Server Client Step 2 : port Server port Client port Connection
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  Types of Socketsin TCP  ServerSocket – the socket used by servers  Socket – Socket used by clients  Create a ServerSocket in the server and make it to wait for connections from Sockets from other clients
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  The concept ofStreams Client output Server input stream stream Client Server socket socket Client input Server output stream stream
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  Socket Programming withUDP  No Connection between client and server.  No handshaking  The sender has to explicitly mention the IP address and the port of the destination.  The server should extract the IP Address of the datagram everytime.  Uses DatagramSocket.
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  Client/server socket interaction: UDP Server Client create socket, create socket, port=x, for clientSocket = incoming request: DatagramSocket() serverSocket = DatagramSocket() Create, address (hostid, port=x), send datagram request using clientSocket read request from serverSocket write reply to serverSocket read reply from specifying client clientSocket host address, port number close clientSocket
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  Coding time..
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  Conclusion  Socket Programmingis very easy in Java.  Usually each and every socket is handled by a separate thread in real-time client/server environments.
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  Queries