Message Send Protocol

One message send service is defined as a connection-based application on TCP. A service listens for TCP connections on port 18. Once a connection is established, a short message is transmitted from the sender to the receiver over the connection. The sender closes the connection after sending the message.

Another message send service is defined as a datagram-based application on UDP. A service listens for UDP datagrams on port 18. When a datagram is received by the receiver, an answering datagram is sent back to the sender containing exactly the same data.

• LAN Messenger
• List of TCP and UDP port numbers
• SMTP