1. Davide Rossi 2002 Using Sockets in Java

2. 2Davide Rossi 2002 TCP/IP  A protocol is a set of rules that determine how things communicate with each other  The software which manages Internet communication follows a suite of protocols called TCP/IP  The Internet Protocol (IP) determines the format of the information as it is transferred  The Transmission Control Protocol (TCP) dictates how messages are reassembled and handles lost information

3. 3Davide Rossi 2002 IP  Internet Protocol: RFC 791  Base protocol for data transmission  It is connectionless and unreliable  It is routable  Defines the addressing of the nodes using IP addresses

4. 4Davide Rossi 2002 IP and Internet Addresses  Each computer on the Internet has a unique IP address, such as: 130.136.1.110  Most computers also have a unique Internet name, which also is referred to as an Internet address: www.cs.unibo.it  The first part indicates a particular computer ( www )  The rest is the domain name, indicating the organization ( cs.unibo.it )

5. 5Davide Rossi 2002 TCP  Transmission Control Protocol: RFC 793  It’s a reliable connection-oriented protocol  Reliability is achieved using packets indexing and generating “ack” messages for each received packet

6. 6Davide Rossi 2002 TCP  Creating a connection is an asymmetrical process; once the connection is established the protocol becomes symmetric  Ports are used to initiate a connection

7. 7Davide Rossi 2002 Connection Sequence FTPHTTP POP 2311080 Server Web Browser Client http://my.server.it my.server.it

8. 8Davide Rossi 2002 TCP Standard Ports  Below 1024, assigned by the IANA 21FTP 23Telnet 80HTTP 110POP3 119NNTP

9. 9Davide Rossi 2002 TCP Connections in Java  The Socket class is used for handling TCP connections in Java  A socket can be used as a data source for a stream  The SocketServer class is used to establish a connection

10. 10Davide Rossi 2002 Waiting for a Connection ServerSocket ss = new ServerSocket(1234); Socket s = ss.accept();

11. 11Davide Rossi 2002 Connecting to a Remote Host Socket s = new Socket(“my.host.it”, 1234);