SNPP or the Simple Network Paging Protocol was developed as an effort to create an Internet communication protocol that would allow for text messages to be passed through the Internet to telecommunication and paging providers. SNPP was initially developed as a one-way solution but it has recently evolved into a protocol capable of supporting two way messaging.

SNPP is a TCP/IP protocol similar to FTP, HTTP, SMTP, etc. The simplest functions provide reliable delivery of a pager identification and an alphanumeric message to a paging system, rather than using an assigned dialup phone line to enter DTMF tones or negotiate a modem connection.

SNPP is a simple way for delivering wireless messages, both one and two-way, to appropriate receiving devices. In its simplest form, SNPP provides a simple way to implement communication between the Internet and a TAP/IXO paging terminal. In its latest form, SNPP provides a method for communicating and receiving end-to-end acknowledgments and replies from two-way messaging devices (such as ReFLEX units).

The SNPP protocol is a sequence of commands and replies, and is based on the philosophy of many other Internet protocols currently in use.

SNPP has several input commands (the first 4 characters of each are significant) that solicit various server responses falling into the following categories:
2xx - Successful, continue
3xx - Begin DATA input (see "DATA" command)
4xx - Failed with connection terminated
5xx - Failed, but continue session SNPP version 3 (two-way) adds the following categories:
7xx - UNsuccessful two-way specific transaction, but continue session
8xx - Successful two-way specific transaction, continue
9xx - Successful QUEUED two-way transaction, continue

The first character of every server response code is a digit indicating the category of response. The text portion of the response following the code may be altered to suit individual applications. The session interaction, especially at SNPP level one, is actually quite simple (hence the name). The client initiates the connection with the listening server. Upon opening the connection, the server issues a "220" level message (indicating the willingness of the server to accept SNPP commands). The client passes pager ID information, and a message, then issues a "SEND" command. The server then feeds the information to the paging terminal, gathers a response, and reports the success or failure to the client.

Sending software that adheres to the SNPP protocol follow the above steps.

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