A TCP client connects to a foreign host on TCP port 1.
It sends the service name followed by a carriage-return line-feed <CRLF>.
The service name is never case sensitive.
The server replies with a single character indicating positive ("+") or negative ("-") acknowledgment,
immediately followed by an optional message of explanation, terminated with a <CRLF>.
If the reply was positive, the selected protocol begins; otherwise the connection is closed.
The name "HELP" is reserved.
If received, the server will output a multi-line message and then close the connection.
The reply to the name "HELP" must be a list of the service names of the supported services, one name per line.
