1. Lab2: Socket Programming Lecturer: Mauro Conti T.A.: Eyüp S. Canlar

2. Exercise 1 Write a client and a multi-threaded server program  Clients send a message to the server Usage: java Lab2Client  Server prints the message out Usage: java Lab2Server

3. Exercise 1: client and server //Client code Socket socket = new Socket(“localhost”, 12345); //Send message …. //Server code ServerSocket servSocket = new ServerSocket(12345); while(true){ Socket cliSocket = servSocket.accept(); //Create a thread to handle //client print request }

4. Exercise 2 Write a program HttpGet.java  Usage: java HttpGet  Requirements: int start(String[] argv)  Initialize Socket, BufferedReader, and BufferedWriter void sendGetRequest(String filename, BufferedWriter out) throws IOException  Send GET request: “GET /path/index.html HTML/1.0\r\n\r\n” void receiveGetResponse(BufferedReader in) throws IOException  Reads the response and prints it line by line on standard output

5. Exercise 2: start(String[] argv) public void start(String[] argv){ try{ Socket socket = new Socket(argv[0]); BufferedReader in = new BufferedReader(new InputStreamReader( socket.getInputStream())); BufferedWriter out = new BufferedWriter(new OutputStreamWriter( socket.getOutputStream()); …. } catch(Exception e){….} }

6. Exercise 2: send and receive Sending GET request  out.write(getRequest); out.flush(); Receiving reply from web server  while (line = in.readln() != null){….}

7. Exercise 3 Modify the program of Exercise 1 to store the received file. To achieve this:  Write a method to parse the path to distil the filename  Send GET request and receive reply  Skip the header of the reply and store the remainder in the local file

8. Exercise 3: parsing the path StringTokenizer strtok = new StringTokenizer(path, “/”); //skip all the tokens until the last one …. filename = strtok.nextToken();

9. Exercise 3: parsing reply while(/*some condition*/){ line = in.readLine(); if(line=“” && !firstEmptyLine){ //We reached the end of the header } if(firstEmptyLine){ //Start reading payload }