Basic Sockets - TCP/IP Sockets in Java Practical Guide for Programmers - page 19

19
20

for (;;) { // Run forever, accepting and servicing connections

21

Socket clntSock = servSock.accept(); // Get client connection

22
23

System.out.println("Handling client at " +

24

clntSock.getInetAddress().getHostAddress()+"onport " +

25

clntSock.getPort());

26
27 InputStream in = clntSock.getInputStream();

28 OutputStream out = clntSock.getOutputStream();

29
30 // Receive until client closes connection, indicated by −1 return

31 while ((recvMsgSize = in.read(byteBuffer)) != −1)

32 out.write(byteBuffer, 0, recvMsgSize);

33
34 clntSock.close(); // Close the socket. We are done with this client!

35

}

36

/* NOT REACHED */

37

}

38 }

TCPEchoServer.java

1. Application setup and parameter parsing: lines 0-12

2. Server socket creation: line 15
servSock listens for client connection requests on the port specified in the constructor.

3. Loop forever, iteratively handling incoming connections: lines 20-35

Accept an incoming connection: line 21
The sole purpose of a ServerSocket instance is to supply a new, connected Socket
instance for each new TCP connection. When the server is ready to handle a client, it
calls accept() , which blocks until an incoming connection is made to the ServerSocket 's
port. accept() then returns an instance of Socket that is already connected to the
remote socket and ready for reading and writing.
Report connected client: lines 23-25
We can query the newly created Socket instance for the address and port of the
connecting client. The getInetAddress() method of Socket returns an instance of
InetAddress containing the address of the client. We call getHostAddress() to return
the IP address as a dotted-quad String . The getPort() method of Socket returns the
port of the client.
Get socket input and output streams: lines 27-28
Bytes written to this socket's OutputStream will be read from the client's socket's
InputStream , and bytes written to the client's OutputStream will be read from this
socket's InputStream .