1. Application Network programming Using Java

2. Application Layer2-2 Socket programming socket: door between application process and end-end-transport protocol Internet controlled by OS controlled by app developer transport application physical link network process transport application physical link network process socket

3. Network Program Overview Reliable traffic (tcp sockets) – Client side (Socket) – Server side (ServerSocket) Unreliable traffic (UDP ‘socket’s) – Client side (DatagramSocket) – Server side (DatagramSocket)

4. Reliable traffic (tcp sockets) wait for incoming connection request connectionSocket = serverSocket.accept() create socket, port= x, for incoming request: serverSocket = socket() create socket, connect to hostid, port= x clientSocket = socket() server (running on hostid ) client send request using clientSocket read request from connectionSocket write reply to connectionSocket TCP connection setup close connectionSocket read reply from clientSocket close clientSocket

5. Essential Java program TCP - Client Socket clientSocket = new Socket(” ”, >) PrintWriter toServer = new PrintWriter(clientSocket.getOutputStream()) Scanner fromServer = new Scanner(clientSocket.getInputStream()) // do work clientSocket.close()

6. TCP – client Python from socket import * serverName = ’servername’ serverPort = 12000 clientSocket = socket(AF_INET, SOCK_STREAM) clientSocket.connect((serverName,serverPort)) sentence = raw_input(‘Input lowercase sentence:’) clientSocket.send(sentence) modifiedSentence = clientSocket.recv(1024) print ‘From Server:’, modifiedSentence clientSocket.close()

7. Server programming

8. Reliable traffic (tcp sockets) wait for incoming connection request connectionSocket = serverSocket.accept() create socket, port= x, for incoming request: serverSocket = socket() create socket, connect to hostid, port= x clientSocket = socket() server (running on hostid ) client send request using clientSocket read request from connectionSocket write reply to connectionSocket TCP connection setup close connectionSocket read reply from clientSocket close clientSocket

9. Essential Java program TCP - Server ServerSocket serverSocket = new ServerSocket( >) LOOP – Socket clientSocket = serverSocket.accept() – PrintWriter toClient = new PrintWriter(clientSocket.getOutputStream()); – Scanner fromClient = new Scanner(clientSocket.getInputStream()); – // do work – clientSocket.close() END LOOP serverSocket.close()

10. TCP – server Python from socket import * serverPort = 12000 serverSocket = socket(AF_INET,SOCK_STREAM) serverSocket.bind((‘’,serverPort)) serverSocket.listen(1) print ‘The server is ready to receive’ while 1: connectionSocket, addr = serverSocket.accept() sentence = connectionSocket.recv(1024) capitalizedSentence = sentence.upper() connectionSocket.send(capitalizedSentence) connectionSocket.close()

11. Client/server socket interaction: UDP close clientSocket read datagram from clientSocket create socket: clientSocket = socket(AF_INET,SOCK_DGRAM) Create datagram with server IP and port=x; send datagram via clientSocket create socket, port= x: serverSocket = socket(AF_INET,SOCK_DGRAM) read datagram from serverSocket write reply to serverSocket specifying client address, port number Application 2-11 server (running on serverIP ) client

12. Essential Java program UDP - Client DatagramSocket clientSocket = new DatagramSocket(); InetAddress IPaddress = InetAddress.getByName(” >”) Int port = > // send request data byte[] sendData = > DatagramPacket sendPacket = new DatagramPacket( sendData, sendData.length, IPaddress, port) clientSocket.send(sendPacket) // receive response data byte[] recvBuffer = new byte[1024] DatagramPacket recvPacket = new DatagramPacket( recvBuffer, recvBuffer.length) clientSocket.receive(recvPacket) clientSocket.close()

13. Essential Java program UDP - Server DatagramSocket serverSocket = new DatagramSocket ( >) LOOP – // receive request data byte[] recvBuffer = new byte[1024] DatagramPacket recvPacket = new DatagramPacket( recvBuffer, recvBuffer.length) – serverSocket.receive(recvPacket) – // do work – // send response data byte[] sendData = > InetAddress IPaddress = recvPacket.getAddress() Int port = recvPacket.getPort() DatagramPacket sendPacket = new DatagramPacket( sendData, sendData.length, IPaddress, port) – serverSocket.send(sendPacket) END LOOP serverSocket.close()

14. UDP – client Python from socket import * serverName = ‘hostname’ serverPort = 12000 clientSocket = socket(socket.AF_INET, socket.SOCK_DGRAM) message = raw_input(’Input lowercase sentence:’) clientSocket.sendto(message,(serverName, serverPort)) modifiedMessage, serverAddress = clientSocket.recvfrom(2048) print modifiedMessage clientSocket.close()

15. UDP – server Python from socket import * serverPort = 12000 serverSocket = socket(AF_INET, SOCK_DGRAM) serverSocket.bind(('', serverPort)) print “The server is ready to receive” while 1: message, clientAddress = serverSocket.recvfrom(2048) modifiedMessage = message.upper() serverSocket.sendto(modifiedMessage, clientAddress)