Add a comment explaining terminal type negociation in telnet

Author: vxgmichel

prompt_toolkit/contrib/telnet/server.py

@@ -62,9 +62,12 @@ def _initialize_telnet(connection: socket.socket) -> None:
  connection.send(IAC + DO + NAWS)
 
  # Negotiate terminal type
+ # Assume the client will accept the negociation with `IAC + WILL + TTYPE`
  connection.send(IAC + DO + TTYPE)
 
- # Negotiate terminal type
+ # We can then select the first terminal type supported by the client,
+ # which is generally the best type the client supports
+ # The client should reply with a `IAC + SB + TTYPE + IS + ttype + IAC + SE`
  connection.send(IAC + SB + TTYPE + SEND + IAC + SE)