Lab2: Socket Programming
Lecturer: Mauro Conti
T.A.: Eyüp S. Canlar
Exercise 1

Write a client and a multi-threaded
server program

Clients send a message to the server


Usage: java Lab2Client <message>
Server prints the message out

Usage: java Lab2Server
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
}
Exercise 2

Write a program HttpGet.java


Usage: java HttpGet <host> <path>
Requirements:

int start(String[] argv)


void sendGetRequest(String filename, BufferedWriter
out) throws IOException


Initialize Socket, BufferedReader, and BufferedWriter
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
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){….}
}
Exercise 2: send and receive

Sending GET request


out.write(getRequest); out.flush();
Receiving reply from web server

while (line = in.readln() != null){….}
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
Exercise 3: parsing the path
StringTokenizer strtok = new
StringTokenizer(path, “/”);
//skip all the tokens until the last one
….
filename = strtok.nextToken();
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
}
}