Question

1. What would happen if change both clientSocket and serverSocket to “mySocket”?

2. Can the client send a segment to server without knowing the server’s IP address and/or port number?

3. Can multiple clients use the server?

From my notes, on page 20 : http://www.cs.ucc.ie/~cjs/teach/cs2505/02-app-layer-b.pdf . Kind of confused with these.

I assume if you change both client and serverSocket to mySocket then nothing would happen, since it would only be a variable name change( I assume ).

And I assume the client can’t send a message without know the IP address/port no?

And that multiple clients cannot use the server since that would require threading?

Answer 1

(1) Since I see no reference to mySocket other than the one in the question I would say your answer seems right.

(2) The address/port are obviously necessary. However this could be a trick question in that client could call connect() on the socket. With UDP, connect() the kernel keeps track of the address passed in the call as the peer of the socket. The socket could then just call write() or send() rather than having to use sendto(). Still, calling connect would still require the address/port in the first place so who knows what they are getting at.

(3) There is no “connection” in UDP. Many clients could send to the server. The server can get the address of the individual clients from its recvfrom and then turn around and use that address in its sendto.