Section notes for CS162 
Section #14, May 6, 2003
Hakim Weatherspoon <hweather@cs.berkeley.edu>

- Administrivia
  - Office hours this week
     Mon 12:00-1:00 6th floor Soda alcove
     Tue 3:30- 4:30 6th floor Soda alcove
  - Project 4 Code Due, Wed 5/14
  - Hand back midterm2 and Project 3 Initial and Final Design Doc
  - Design Reviews Wed 5/7/2003 from 9:00am-4:00pm.  15 minutes each.
  - I will be out of town Thurs 5/8/2003 - Mon 5/12/2003.
  - Project 4 Design Docs
    Documents should be a 9 +- 1 PAGE.

QUIZ
We have a star topology network where the center node is a broadcast
server.  The edge nodes can send a msg to the server that will be
broadcast to all other edge nodes. 

What state is needed per client?
  connected
  file descriptor for connection
  name
  msg buffer
  size of msg in buffer

Given that we can only use static size buffers and that 
the call to read may not return a complete msg, how does
the server make sure that it has all the bytes for a msg before
broadcasting msg to other nodes?  Write solution in pseudocode
(The header of a msg includes a length [integer])

  That is read(fd, buffer, size) may return less than size bytes.

  1) readBytes = read(client_fd, client_buf+client_buf_sz, 
                      MAX_BUF_SZ - client_buf_sz);
 
  2) msg_length = (int)client_buf; // first four bytes;
     length = msg_length + sizeof(int);

     if(client_buf_sz >= length) {
       broadcast( client_buf, length );
       client_buf_sz -= length;
       memcpy(client_buf, &client_buf[length], client_buf_sz);
     }

What are the errors?
  readBytes returns -1 (close connection).

  
Project 4 
II Chat UI Expectation
1) Client sends msg to server when user hits enter ('\n');
   Do not echo msg on the clients console who sent msg.
2) On a received msg:
   display username at start of line (i.e. user that sent msg) and rest of
   msg.
3) You do not need malloc.  Use all static size buffers.
   You can assume 80 characters per line and no more than three clients.
4) We will first test their chat on their Nachos implementation.
   If that does not work, we will test their chat on our Nachos
4) Data Structures:
     Server -
       struct per client
       includes fd, name, buffer, size
     Client -