What is XMPP? Functions and benefits at a glance

With the open XMPP protocol, you don’t need your own messenger service to com­mu­ni­cate with other users. Based on the XML standard, XMPP enables device- and browser-in­de­pen­dent com­mu­ni­ca­tion via an XMPP client and XMPP server or XMPP-com­pat­i­ble services. Thanks to secure en­cryp­tion and functions for audio/video calls, XMPP offers a flexible chat and instant messaging al­ter­na­tive.

XMPP is an ab­bre­vi­a­tion for 'Ex­ten­si­ble Messaging and Presence Protocol', which refers to an ex­ten­si­ble messaging and presence protocol for online com­mu­ni­ca­tion. The fun­da­men­tals of XMPP are the client-server principle and the open XML standard, in which an XMPP client on the user’s terminal com­mu­ni­cates with other par­tic­i­pants via an XMPP server.

XMPP tech­nol­o­gy has been developed by Jeremie Miller since 1998. The first major XMPP version, then still called Jabber, was released in 2000. With real-time streaming protocol based on the XML standard, the open-source software presented itself as a free, flexible al­ter­na­tive to com­mer­cial instant messaging. In 2004, Jabber became the XMPP standard protocol, modified by the IETF (Internet En­gi­neer­ing Task Force), which is main­tained and stan­dard­ised in new im­ple­men­ta­tions by the XMPP Standards Foun­da­tion.

The way XMPP works is based on the exchange of in­for­ma­tion between a client and a server. This means that in order to use XMPP and establish a con­nec­tion, free XMPP client software is required first. Examples of this are:

• Miranda and Gajim (Windows)
• Pidgin (Linux, Windows)
• Dino (Linux)
• Con­ver­sa­tions (Android)
• Coc­cinel­la (iOS)

With a client, you can even exchange messages with messenger services and email services that support the XMPP protocol, view par­tic­i­pant status, use group chats and make audio/video calls. Other handy features include for­ward­ing for emails and SMS, transport con­nec­tions to other IM networks, and RSS feed man­age­ment. XMPP servers act similarly to SMTP servers and mail transfer agents, which act as a com­mu­ni­ca­tion interface to receive and send messages between par­tic­i­pants.

To use XMPP, you need an account from a cor­re­spond­ing XMPP provider. One account is usually enough as com­mu­ni­ca­tion takes place across different XMPP servers. To register, you create a username and password and receive a J-ID (Jabber Iden­ti­fi­er), which is like an email address for iden­ti­fi­ca­tion and ad­dress­ing in the network: username@example.com. The @ is preceded by the username and followed by the cor­re­spond­ing reg­is­tra­tion server.

Using your own J-ID, you log in to the ap­pro­pri­ate client, create an XMPP account, and use your XMPP client to connect to one of the many XMPP servers or log in to the server of your choice. This in turn connects you to the server of other par­tic­i­pants and es­tab­lish­es com­mu­ni­ca­tion. It is even possible to implement XMPP for isolated, internal intranets.

The open XMPP protocol offers the following features to its users:

With XMPP im­ple­men­ta­tions, you can send instant messages in­de­pen­dent of the operating system and browser, rather than relying on pro­pri­etary instant mes­sen­gers.

Peer-to-peer sessions are possible with an extension called Jingle, which is similar to the way the Session Ini­ti­a­tion Protocol works and can also be used for VoIP telephony. Other Jingle functions are con­nec­tions via “Jingle Signaling” via Network Address Trans­la­tions (NAT) as well as User Datagram Protocol (UDP).

With the ap­pro­pri­ate client, you can also com­mu­ni­cate with par­tic­i­pants in real time via audio and video call, similar to other messenger services.

Con­fer­ences and group sessions are possible with XMPP spec­i­fi­ca­tions such as multi-user chat and functions like chat rooms or chat groups. Here, roles can be assigned, or rooms can be password protected and made invisible. The principle is similar to IRC (Internet Relay Chat).

XMPP Trans­ports allows users to com­mu­ni­cate with par­tic­i­pants in other networks such as ICQ, IRC, Yahoo Messenger or AOL Instant Messenger via the XMPP server without XMPP users having to access the third-party server directly. Messages are sent from the XMPP server to XMPP trans­ports and forwarded from there to the third-party servers of other par­tic­i­pants. If the third-party server is on a network that is not XMPP-compliant, you must have an account on that network and XMPP clients that support service discovery and provide com­mu­ni­ca­tion with pro­pri­etary instant mes­sen­gers.

For security reasons, XMPP con­nec­tions should be encrypted, since security vul­ner­a­bil­i­ties for a man-in-the-middle attack or phishing can occur when con­nect­ing from one server to another. En­cryp­tion is possible, for example, via TLS (Transport Layer Security) according to the client-to-server en­cryp­tion principle. However, for optimum security and as few points of attack as possible, a com­bi­na­tion of client-to-server and server-to-server en­cryp­tion is rec­om­mend­ed. The highest level of security is provided by end-to-end en­cryp­tion, in which data is encrypted by the sender client and decrypted by the recipient client. In this case, even servers are unable to decrypt trans­mit­ted data. The OMEMO protocol is often used here.

The open-source XMPP protocol served as the basis for many pro­pri­etary messenger services, some of them former, such as Google Talk, ICQ or Yahoo Messenger, and therefore enabled rel­a­tive­ly free com­mu­ni­ca­tion between different mes­sen­gers. Although common pro­pri­etary instant messaging services no longer offer support for XMPP/Jabber, mes­sen­gers such as WhatsApp, Facebook Messenger or iMessage use variants of the XMPP protocol. XMPP has by no means lost in pop­u­lar­i­ty and dis­tri­b­u­tion in view of thousands of servers for XMPP and numerous clients with an XMPP spe­cial­iza­tion.

XMPP offers the great advantage that suitable clients can be found for the most common operating systems and that almost every pro­gram­ming language is supported. Another advantage is that it means you don’t have to use pro­pri­etary messenger software whose privacy policies and non-trans­par­ent use of user data don’t meet your needs. In addition, XMPP com­mu­ni­ca­tion offers the pos­si­bil­i­ty to forward emails and SMS or to com­mu­ni­cate with others via video, audio or IP telephony. End-to-end en­cryp­tion can be used for reliable security.