Connection State in Socket Calls

Client
- when socket is created, the connection is in CLOSED state
- when connect() is called, TCP initiates the 3-ways handshake and the status change to CONNECTING.
- when the 3-way hand shake completes, the connection status change to ESTABLISHED
- 2 possible errors
- ETIMEDOUT = TCP does not received a response from server for the handshake even with retransmission
- ECONNREFUSED = server sends a RESET packet which could means the socket server is not listening

Server
- when the socket is created, the connection is in CLOSED state
- when bind() is called, the local Iport is filled in the socket structure.  STatus is still CLOSED
- when listen() is called, status change to LISTENING
- when client request comes in, a new socket structure is allocated with the local IP address (remember the request can come in multiple interfaces of the servers) and the remote IP/port.  Status changed to CONNECTING.
- When the 3-way handshake completed, the status changed to ESTABLISHED
- when accept() is called, the new socket descriptor is returned to the caller.