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.