CSCE 515: Computer Network Programming Chin-Tser Huang University of South Carolina

1/22/20042 TCP Sockets in Java Use class Socket and class ServerSocket An instance of Socket represents one end of a TCP connection An instance of ServerSocket listens for client requests and creates a new Socket instance to handle each incoming connection Both client and server use Socket to send and receive messages

1/22/20043 Class Socket Constructors Socket(String host, int port) throws IOException Socket(InetAddress address, int port) throws IOException Socket(String host, int port, InetAddress localAddr, int localPort) throws IOException Socket(InetAddress address, int port, InetAddress localAddr, int localPort) throws IOException

1/22/20044 Class Socket Methods InputStream getInputStream() throws IOException OutputStream getOutputStream() throws IOException void close() throws IOException InetAddress getInetAddress() int getPort() InetAddress getLocalAddress() int getLocalPort()

1/22/20045 Class Socket Methods void setSoTimeout(int timeout) throws SocketException int getSoTimeout() throws SocketException void setTcpNoDelay(boolean on) throws SocketException boolean getTcpNoDelay() throws SocketException void setSoLinger(boolean on, int val) throws SocketException int getSoLinger() throws SocketException void setSendBufferSize(int size) throws SocketException int getSendBufferSize() throws SocketException void setReceiveBufferSize(int size) throws SocketException int getReceiveBufferSize() throws SocketException

1/22/20046 Class Socket Exceptions IOException SocketException BindException ConnectException NoRouteToHostException SecurityException

1/22/20047 A TCP Echo Client Example Construct a socket with specified server and port Communicate with the server using the socket’s I/O streams Display the echo from server Close the connection with server

1/22/20048 TCPEchoClient.java /* * TCP/IP Sockets in Java * Kenneth Calvert, Michael Donahoo * Morgan Kaufmann Publishers; ISBN * * de.html* * Copyright (c) 2002 Kenneth Calvert, Michael Donahoo ; * all rights reserved; see license.txt for details. */ import java.net.*; import java.io.*; public class TCPEchoClient { // public static void main (String args[]) … }

1/22/20049 Method main public static void main(String[] args) throws IOException { if ((args.length 3)) // Test for correct # of args throw new IllegalArgumentException("Parameter(s): [ ]"); String server = args[0]; // Server name or IP address // Convert input String to bytes using the default character encoding byte[] byteBuffer = args[1].getBytes(); int servPort = (args.length == 3) ? Integer.parseInt(args[2]) : 7; // Create socket that is connected to server on specified port Socket socket = new Socket(server, servPort); System.out.println("Connected to server...sending echo string"); InputStream in = socket.getInputStream(); OutputStream out = socket.getOutputStream(); out.write(byteBuffer); // Send the encoded string to the server …

1/22/ Method main (cont’d) // Receive the same string back from the server int totalBytesRcvd = 0; // Total bytes received so far int bytesRcvd; // Bytes received in last read while (totalBytesRcvd < byteBuffer.length) { if ((bytesRcvd = in.read(byteBuffer, totalBytesRcvd, byteBuffer.length - totalBytesRcvd)) == -1) throw new SocketException("Connection close prematurely"); totalBytesRcvd += bytesRcvd; } System.out.println("Received: " + new String(byteBuffer)); socket.close(); // Close the socket and its streams }

1/22/ Class ServerSocket Constructors ServerSocket(int port) throws IOException ServerSocket(int port, int backlog) throws IOException ServerSocket(int port, int backlog, InetAddress bindAddr) throws IOException

1/22/ Class ServerSocket Methods Socket accept() throws IOException void close() throws IOException InetAddress getInetAddress() int getLocalPort() Void setSoTimeout(int timeout) throws SocketException Int getSoTimeout() throws IOException

1/22/ Class ServerSocket Exceptions IOException SecurityException

1/22/ A TCP Echo Server Example Construct a server socket specifying local port to be listened to Repeatedly do the following Accept the next client connection request and create a socket for this connection Communicate with the client using the socket’s I/O streams Close the connection with client

1/22/ TCPEchoServer.java /* * TCP/IP Sockets in Java * Kenneth Calvert, Michael Donahoo * Morgan Kaufmann Publishers; ISBN * * de.html* * Copyright (c) 2002 Kenneth Calvert, Michael Donahoo ; * all rights reserved; see license.txt for details. */ import java.net.*; import java.io.*; public class TCPEchoServer { private static final int BUFSIZE = 32; // Size of receive buffer // public static void main (String args[]) … }

1/22/ Method main public static void main(String[] args) throws IOException { if (args.length != 1) // Test for correct # of args throw new IllegalArgumentException("Parameter(s): "); int servPort = Integer.parseInt(args[0]); // Create a server socket to accept client connection requests ServerSocket servSock = new ServerSocket(servPort); int recvMsgSize; // Size of received message byte[] byteBuffer = new byte[BUFSIZE]; // Receive buffer …

1/22/ Method main (cont’d) for (;;) { // Run forever, accepting and servicing connections Socket clntSock = servSock.accept(); // Get client connection System.out.println("Handling client at " + clntSock.getInetAddress().getHostAddress() + " on port " + clntSock.getPort()); InputStream in = clntSock.getInputStream(); OutputStream out = clntSock.getOutputStream(); // Receive until client closes connection, indicated by -1 return while ((recvMsgSize = in.read(byteBuffer)) != -1) out.write(byteBuffer, 0, recvMsgSize); clntSock.close(); // Close the socket. We are done with this client! } /* NOT REACHED */ }

1/22/ Next Class UDP sockets Non-blocking Read JNP Ch. 16, 20