This project implements an MSRP Relay. Its main role is to help NAT traversal of MSRP based Instant Messaging and File Transfer sessions between SIP end-points located behind NAT. This extension is defined in RFC 4976.

This software is licensed according to the GPL version 2.


A series of related instant messages between two or more parties can be viewed as part of a "message session", that is, a conversational exchange of messages with a definite beginning and end. This is in contrast to individual messages each sent independently. Messaging schemes that track only individual messages can be described as "page-mode" messaging, whereas messaging that is part of a "session" with a definite start and end is called "session-mode" messaging.

Page-mode messaging is enabled in SIP via the SIP MESSAGE method, as defined in RFC 3428. Session-mode messaging has a number of benefits over page-mode messaging, however, such as explicit rendezvous, tighter integration with other media-types, direct client-to-client operation, and brokered privacy and security.

Message Session Relay Protocol (MSRP) is a protocol for transmitting a series of related instant messages in the context of a session. Message sessions are treated like any other media stream when set up via a rendezvous or session creation protocol such as the Session Initiation Protocol (SIP). MSRP Sessions are defined in RFC 4975.


  • Multiple domains support
  • TLS encryption and digital certificates using GnuTLS library
  • Digest or basic HTTP authentication with support for multiple realms
  • Database passwords can be stored in an encrypted format

Clients that support MSRP relay extension


Curent version is 1.1.0 released on 29 April 2015. The relay is used in production since 2009.


The project is supported via this wiki collaboration system. To open ticket please Register first. The ticketing support system is available only for registered users. The support is provided on a best-effort basis.

Help is also provided on the SIP Beyond VoIP mailing list

Commercial support

The software is supported commercially by AG Projects.


Authors: Adrian Georgescu, Ruud Klaver, Dan Pascu, Saúl Ibarra

The development of MSRP relay has been sponsored by NLNet foundation

MSRP-Relay-Scenarios.png (49 kB) Tijmen de Mes, 04/03/2012 02:48 pm