Network Working Group R. Nelson
Request for Comments: 1159
Message Send Protocol
Status of this Memo
This RFC suggests an Experimental Protocol for the Internet
community. Hosts on the Internet that choose to implement a Message
Send Protocol may experiment with this protocol. Please refer to the
current edition of the "IAB Official Protocol Standards" for the
standardization state and status of this protocol. Distribution of
this memo is unlimited.
The Message Send Protocol is used to send a short message to a given
user on a given terminal on a given host. This is similar to the
service provided by Unix's write command, which is limited to the
users on that host. This service is also known on some hosts as
As the Internet grows, more and more people are using hosts that do
not run TCP/IP at all times. These hosts may be able to use a simple
protocol that can be implemented in a subset of TCP/IP. The Message
Send Protocol is one such protocol.
Note that a message sending protocol is already defined using TCP.
The SMTP protocol includes a "SEND" command that will direct mail to
a user's terminal. SMTP's SEND is not useful in this instance
because TCP requires quite a bit of code. For the purposes of
standardization, we will include a TCP based Message Send Service.
TCP Based Message Send Service
One message send service is defined as a connection based application
on TCP. A server listens for TCP connections on TCP port 18. Once a
connection is established a short message is sent by the client out
the connection (and any data received by the client is thrown away).
The client closes the connection after sending the message.
UDP Based Message Send Service
Another message send service is defined as a datagram based
application on UDP. A server listens for UDP datagrams on UDP port
18. When a datagram is received by the server, an answering datagram