Socket programming 1

1. Socket programming 1

2. getByName import java.net.*; public class GetHostName { public static void main (String args[]) { String host = "www.concordia.ca"; try { InetAddress address = InetAddress.getByName(host); System.out.println(address); } catch (UnknownHostException e) { System.out.println("Could not find "+ host); } } }

3. getByName import java.net.*; public class GetNameByAddress { public static void main (String args[]) { try { InetAddress address = InetAddress.getByName("132.205.7.63"); System.out.println(address); } catch (UnknownHostException e) { System.out.println("Could not find 132.205.7.63"); } } }

4. LocalMachineAddress import java.net.*; public class LocalMachineAddress { public static void main (String args[]) { try { InetAddress address = InetAddress.getLocalHost(); System.out.println(address); } catch (UnknownHostException e) { System.out.println("Could not find this computer's address."); } } }

5. Local machine name import java.net.*; public class LocalMachineName { public static void main (String args[]) { try { InetAddress address = InetAddress.getLocalHost(); System.out.println("Local Machine Name is " + address.getHostName()); } catch (UnknownHostException e) { System.out.println("No Name for this machine."); } } }

6. Elementary TCP socket TCP Server TCP Client ServerSocket() Well-known port Bind() Listen() Accept() Socket() Blocks until connections from client Connect() Connection establishment (TCP 3-way Handshake) Write() Read() Data (request) Process request Write() Data (reply) Read() Close() Close() Socket functions for elementary TCP client-server

7. ServerSocket • ServerSocket(int port)           Creates a server socket, bound to the specifie port. Back

8. Listen • accept() method of ServerSocket instance object returns Socket instance object.           Accept method listens for a connection to be made to this socket and accepts it. Back

9. Read from a socket • DataInputStream • A data input stream lets an application read primitive Java data types from an underlying input stream in a machine-independent way. • An application uses a data output stream to write data that can later be read by a data input stream. • readUTF() method return String data type • It reads from the stream in a representation of a Unicode character string encoded in Java modified UTF-8 format; this string of characters is then returned as a String. The details of the modified UTF-8 representation are exactly the same as for the readUTF method of DataInput.

10. getInputStream() method of Socket class • getInputStream() method of class socket          Returns an input stream type (InputStream) for this socket. • If this socket has an associated channel then the resulting input stream delegates all of its operations to the channel. Back

11. Write to a socket • DataOutputStream class • A data output stream lets an application write primitive Java data types to an output stream in a portable way. • An application can then use a data input stream to read the data back in. • writeUTF() method writes a string to the underlying output stream using Java modified UTF-8 encoding in a machine-independent manner.

12. getOutputStream() method of Socket class • getOutputStream() method of Socket class returns an output stream for this socket. • If this socket has an associated channel then the resulting output stream delegates all of its operations to the channel. Back

13. Socket • Socket(InetAddress address, int port)           Creates a stream socket and connects it to the specified port number at the specified IP address. Back

14. TCPServer import java.net.*; import java.io.*; public class TCPServer { public static void main (String args[]) { try{ int serverPort = 7896; // the server port ServerSocket listenSocket = new ServerSocket(serverPort); while(true) { Socket clientSocket = listenSocket.accept(); Connection c = new Connection(clientSocket); } } catch(IOException e) {System.out.println("Listen socket:"+e.getMessage());} } } class Connection extends Thread { DataInputStream in; DataOutputStream out; Socket clientSocket; public Connection (Socket aClientSocket) { try { clientSocket = aClientSocket; in = new DataInputStream( clientSocket.getInputStream()); out =new DataOutputStream( clientSocket.getOutputStream()); this.start(); } catch(IOException e) {System.out.println("Connection:"+e.getMessage());} } public void run(){ try { // an echo server String data = in.readUTF(); // read a line of data from the stream out.writeUTF("Thats what i received from you :"+ data); }catch (EOFException e){System.out.println("EOF:"+e.getMessage()); } catch(IOException e) {System.out.println("readline:"+e.getMessage()); } finally{ try {clientSocket.close();}catch (IOException e){/*close failed*/}} } }

15. TCPClient import java.net.*; import java.io.*; public class TCPClient { public static void main (String args[]) { // arguments supply message and hostname Socket s = null; try{ intserverPort = 7896; s = new Socket("127.0.0.1", serverPort); DataInputStream in = new DataInputStream( s.getInputStream()); DataOutputStream out =new DataOutputStream( s.getOutputStream()); out.writeUTF("127.0.0.1"); // UTF is a string encoding see Sn. 4.4 String data = in.readUTF(); // read a line of data from the stream System.out.println("Received: "+ data) ; }catch (UnknownHostException e){System.out.println("Socket:"+e.getMessage()); }catch (EOFException e){System.out.println("EOF:"+e.getMessage()); }catch (IOException e){System.out.println("readline:"+e.getMessage()); }finally {if(s!=null) try {s.close();}catch (IOException e){System.out.println("close:"+e.getMessage());} } }

16. References • http://www.ibiblio.org/java/books/jnp/javanetexamples/index.html • Java Docummentation. • http://users.encs.concordia.ca/~s423_2/CodeSample/Sockets/Text%20Book/