Message Send Protocol
The Message Send Protocol (MSP) is an application layer protocol used to send a short message between nodes on a network. The original version of the protocol was published in 1990.{{Cite IETF |title=Message Send Protocol |rfc=1159 |last1=Nelson |first1=Russell |date=June 1990 |publisher=IETF |doi=10.17487/RFC1159}} It was updated as Message Send Protocol 2 in 1992.{{Cite IETF |title=Message Send Protocol 2 |rfc=1312 |last1=Nelson |first1=Russell |last2=Arnold |first2=Geoff |date=April 1992 |publisher=IETF |doi=10.17487/RFC1312}}
TCP-based service
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.