1. Socket programming with UDP and TCP

2. Socket Programming with TCP Connection oriented – Handshaking procedure Reliable byte-stream

3. TCP-client in Java import java.io*; import java.net.*; Class TCPClient { public static void main (String argv[]) throws Exception { String sentence; String modifiedSentence; BufferedReader inFromUser = new BufferedReader( new InputStreamReader(system.in)); Socket clientSocket = new Socket(”hostname”, 6789); DataOutpuStream outToServer = new DataOutputStream( clientSocket.getOutputStream()); BufferedReader inFromServer = new BufferedReader(new InputStreamReader( clientSocket.getInputStream())); sentence = inFromUser.readLine(); outToServer.writeBytes(sentence + ’\n’); modifiedSentence = inFromServer.readLine(); System.out.println(”FROM SERVER: ” + modifiedSentence); clientSocket.close(); } }

4. TCP-client in Java import java.io*; import java.net.*; Imports needed packages Class TCPClient { public static void main (String argv[]) throws Exception { Standard Java initiation

5. TCP-client in Java String sentence; String modifiedSentence; Declares two string objects BufferedReader inFromUser = new BufferedReader( new InputStreamReader(system.in)) Creates a stream that handels input from the user

6. TCP-client in Java Socket clientSocket = new Socket(”hostname”, 6789) ; Initiate a TCP-connection with the ”hostname” through port 6789 Client performes a DNS lookup to obtain host IP. DataOutpuStream outToServer = new DataOutputStream( clientSocket.getOutputStream()) Creates a stream that handels output to server

7. TCP-client in Java BufferedReader inFromServer = new BufferedReader(new InputStreamReader( clientSocket.getInputStream())); Creates a stream that handels input from server sentence = inFromUser.readLine() Puts the input from user into string object

8. TCP-client in Java outToServer.writeBytes(sentence + ’\n’); Transform sentence to bytes & sends to server modifiedSentence = inFromServer.readLine(); Puts input from server into modified sentence System.out.println(”FROM SERVER: ” + modifiedSentence); clientSocket.close(); } } Prints modifiedSentence and closes the connection

9. TCP-server in Java import java.io*; import java.net.*; Class TCPServer { public static void main (String argv[]) throws Exception { String clientSentence; String capitalizedSentence; ServerSocket welcomeSocket = new ServerSocket (6789); while (true) { Socket connenctionSocket = welcomeSocket.accept(); BufferedReader inFromClient = new BufferedReader( new InputStreamReader( connectionSocket.getInputStream())); DataOutpuStream outToClient = new DataOutputStream( connectionSocket.getOutputStream()); clientSentence = inFromClient.readLine(); capitalizedSentence = clientSentence.toUpperCase() + ’\n’; outToClient.writeBytes(capitalizedSentence); }}}

10. TCP-server in Java ServerSocket welcomeSocket = new ServerSocket (6789); Creates a welcomeSocket that handels connection-attempts from port 6789 Socket connenctionSocket = welcomeSocket.accept(); Creates a new socket

11. TCP-server in Java capitalizedSentence = clientSentence.toUpperCase() + ’\n’; This command is the essence of the application.

12. Socket Programming with UDP Connectionless No reliable datatransfer

13. UDP-client in Java import java.io.*; import java.net.*; class UDPClient { public static void main(String args[ ]) throws Exception { BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in)); DatagramSocket clientSocket = new DatagramSocket(); InetAddress IPAddress = InetAddress.getByName(”hostname”); byte[ ] sendData = new byte[1024]; byte[ ] recieveData = new byte[1024]; String sentence = inFromUser.readLine(); sendData = sentence.getBytes (); DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876); clientSocket.send(sendPacket); DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length); clientSocket.receive(receivePacket); String modefiedSentence = new String(receivePacket.getData()); System.out.println(”FROM SERVER:” + modifiedSentence); clientSocket.close();}

14. UDP-client in Java DatagramSocket clientSocket = new DatagramSocket(); This line does not initiate a TCP connection InetAddress IPAddress = InetAddress.getByName(”hostname”); Uses DNS lookup to find the IP-address for ”hostname”

15. UDP-client in Java byte[ ] sendData = new byte[1024]; byte[ ] recieveData = new byte[1024]; Arrays that contains bytes that will be sent and recieved DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876); Creates a packages that containes travel information

16. UDP-client in Java clientSocket.send(sendPacket); Sends the package through the client socket DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length); Creates a placeholder for the package clientSocket.receive(receivePacket); Rececives the package from the server

17. UDP-client in Java String modefiedSentence = new String(receivePacket.getData()); Extracts the data from the package and puts it in a string package clientSocket.close(); Closes the client socket

18. UDP-server in Java import java.io.*; import java.net.*; class UDPClient { public static void main(String args[ ]) throws Exception { DatagramSocket serverSocket = new DatagramSocket(9876); byte[ ] receiveData = new byte[1024]; byte[ ] sendData = new byte[1024]; while(true) { DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length); serverSocket.receive(receivePacket); String sentence = new String(receivePacket.getData()); InetAddress IPAddress = receivePacket.getAddress(); int port = receivePacket.getPort(); String catitalizedSentence = sentence.toUpperCase(); sendData = capetalizedSentence.getBytes (); DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port); clientSocket.send(sendPacket); DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length); serverSocket.send(sendPacket); }}}

19. UDP-server in Java DatagramSocket serverSocket = new DatagramSocket(9876); Creates a socket at port 9876 that data passes through String sentence = new String(receivePacket.getData()); InetAddress IPAddress = receivePacket.getAddress(); int port = receivePacket.getPort(); Extracts the data and client information from the package