added help argument

src/clientP2P/ClientP2P.java

@@ -71,6 +71,11 @@ public class ClientP2P {
 	 * @param args	server listenning port
 	 */
 	public static void main(String [] args) {
+
+		if (args[1].equals("help") || args[1].equals("-h") || args[1].equals("h")){
+			System.out.println("usage : java -ea clientP2P.ClientP2P -- <PORT> ");
+		}
+		else{
 			ClientP2P c;
 			try {
 				c = new ClientP2P(args[1]);
@@ -125,3 +130,4 @@ public class ClientP2P {
 			t.start();
 		}
 	}
+}