What is XMPP ❓ — Extensible Messaging & Presence Protocol

Ivan Novikov
8 min readJan 25, 2022


In the early 2000s, when the idea of chat applications was shaping, XMPP was allowing developers to construct interactive chat applications. Since its genesis, this protocol has come a long way and is now included in the tech stack (or framework) suggested for developing high-end chat apps like WhatsApp.

More than two decades later too, this protocol hasn’t lost its sheen and significance in the abundance of the protocol. Why is it so? What makes XMPP time relevant? What are the key markers? Let’s know this protocol a little better.

What is XMPP — Extensible Messaging & Presence Protocol?

It is an XML-driven protocol utilized typically in open standard communication. To say it concisely, it is a chat protocol that permits the seamless to and fro sending of essential XML components such as data. Besides making IM and real-time ‘talks’ possible, XMPP also finds its applications in contact list maintenance and presence details.

The Usage

XMPP is most generally used in forthright message interaction between two points, checking the user status, sharing the status details with the server. It also takes care of server status record keeping, subscription management, contact list updates, and blockading certain users.

The Attributes

  • It’s decentralized.
  • It supports the asynchronous exchange of data/information.
  • Transmits tiny pieces of the data instead of forwarding the big chunks directly.
  • It works over TCP.
  • Network configuration and components (hardware/software) has no role to play in the XMPP-based data transmission.
  • It is designed for client-server model.
  • It uses 3 statuses, namely ‘offline’, ‘busy’, or ‘online’, to tell about the status of a user or network.
  • It transfers data back and forth between two end-points.

XMPP Architecture

On a structural level, XMPP shares great similarities with protocols that work on the application layer. For example, it also concerns uniquely named clients communicating over an associated server. Enforcing the protocol as per both clients, XMPP monitors and handles routing for them.

The overhead figure illustrates the XMPP architecture straightforwardly.

However, in a complex implementation, multiple XMPP gateways might also exist. In this scenario, the protocol also needs to takes care of the intercommunication for multiple domain routing. So, the gateways act as a translating medium between various protocols and domains that are in the cycle during the information-exchange.

Additionally, the XMPP gateway brooks the tasks like commencing and termination of the client-to-server sessios at the intended protocol while including the demanding protocol translation elements.

Even with the use of considerable gateways and domains, one can succeed in achieving constant connectivity across all the network points with the help of XMPP.

While comprehending the XMPP architecture, understanding a few terms is crucial.

For example, you must know about XMPP stanzas. These, simply, are the small XML fragments that are used for starting a communication session. they can be of 3 types:

  • The presence stanza defines the network or user’s present status to others. For example, the user/network is online or offline.
  • Message stanza is a pushing instrument essential for chat messages exchange.
  • IQ stanza is the element that XMPP utilizes for data requests and modification. Just as HTTP has GET and POST, XMPP has IQ stanza.

How does XMPP protocol work?

The entire processing of XMPP relies upon the client-server architecture that interests message transmission to the server first and then to the clients.

To find out which client should receive the message, the XMPP server utilizes the unique ID of the receiver. The unique ID or Jabber ID is very much comparable to an email address with negligible changes.

user@domain.com/resource is the format for the Jabber ID.

Here, the user directs to the username, domain.com is the domain particulars of the sender, and resource is the device type of message receiver. For example,


In the example, John Ray is the user name, Technology.testing is the domain name, and terminal is the type of device or resource that is used by John. The resource is an optional part while the previous two are essential.

XMPP server employs this Jabber ID for correct message routing over TCP connection. As soon as a communication session is started, an XML stream is shared to the server and client identification is done with the help of Jabber ID.

Once the identification is done, the server will receive the request and will initiate another XML stream transmission request. This stream will be sent back to the client from the server’s side. This way, each XML stream becomes bi-directional.

XMPP is efficient to generate a large-scale message network known as a federation. With the help of a federation, clients can communicate with multiple XMPP servers at a time.

XMPP Features

Fundamental features that make XMPP stand out from other protocols are as under:

  • Asynchronous Push Messaging

With XMPP, continual and asynchronous message delivery is achievable. With this, we mean message dispatch in a row, not waiting for the receiver or sender reply, and not necessitating the user to be online to accept the message. Messages are shared in the form of XML stanzas that are distinctive information units featuring segments like metadata, message body, and unique ID of the sender & receiver.

What makes XMPP distinguishable from other client-server systems is that XMPP doesn’t support polling. Polling is the process where the client prompts the server constantly to review whether or not any recent information is present. As polling is done at regular intervals, there is no instant communication experience for end-users. Also, it ushers in outrageous bandwidth consumption.

Rather, XMPP automatically propels the recent message to the server even when the previous request is not processed or received by the server. It happens in the server-to-client side of communication as well. This constructs an instant communication experience for users.

  • Client-Server Architecture

This is the core architecture that XMPP follows. In this architecture, XMPP disseminates only a small fraction of XML elements. This portative XML element will first reach to the server and then to the user.

The XMPP clients are allocated separate names, just like an email. This unique ID is used to recognize the client and route the message in the right direction. This way, XMPP guarantees that each XMPP client observes a fixed and standard route to couple with the server.

  • Persistent TCP Connections

Originally, XMPP can transmit the data or designate a connection over TCP only. Connection built over here is invariant and doesn’t demand re-establishment whenever a new message is transmitted.

This way, XMPP constructs an XML stream supporting free XML data exchange. However, certain cutting-edge XMPP extensions now use TLS and WebSockets as well.

  • Decentralized Hosting

With decentralized hosting, we refer to having no central authority controlling the server. Anyone can maintain, run, and even maintain the XMPP servers. Additionally, freedom to set up the servers on either cloud or premise is also granted. On this front also, it’s similar to email. Every email owner can set up emails as per their choices. They have the freedom to set up the login details, password, and other details as per their preferences.

  • Gateways

One another very distinguishing feature of XMPP is that it offers gateways for numerous chats and messaging protocols. It’s compatible with many protocols and can link to the networks at length.

For instance, a given XMPP network can access an SMS domain when a message is supplied to the receiver on the mobile and simultaneously to the SMTP domain to deliver the same message on the receiver’s email. In addition to this, the XMPP network to deliver the message in another form, say IRC, can also use any other particular message protocol, concurrently.

XMPP Protocol Example

XMPP enjoys the reputation of a core element for many communication apps that we use presently. Some of the most famed apps, developed using XMPP, are as mentioned below.

  • WhatApp is built using a proprietary XMPP.
  • The amazing chat capability of Zoom is all because of XMPP.
  • For instant push notification delivery, Apple uses XMPP both in the iPhone and Mac.
  • XMPP is used in the chat functionality of Grindr.

For development of highly functional chat apps, XMPP is one of the multiple choices offered. However, it continues to grow as a preferred one for many because of its distinctive features and multiple benefits that it brings on the table.

Benefits of XMPP

Backed by IETF and embraced by thousands of developers, XMPP has become a mainstream open standard protocol for chat application development.

With outstanding markers, XMPP contrived to fill the gap, assembled by stringent protocols, and has affirmed itself as a necessity for peer-to-peer communication and beyond.

Below are the fundamental benefits to enjoy after adopting the XMPP protocol.

  • A Reliable Protocol to Back upon

This protocol has been serving the developer community for more than 20 years. Through these years, the protocol has strengthened its infrastructure and gained huge community backing. Presently, multiple XMPP servers are out there, thousands of developers have used it, and it is at the core of many applications.

All of this ensures that this protocol is time-tested and has great technical support. If that doesn’t impress you then being free and too straightforward will surely do.

  • Improves Communication Infrastructure for you

Being a highly extensible protocol, it enables end-users to use it in communicating different sorts of media and messages. It won’t ask you whether you’re transmitting audio or a video; XMPP will continue to support in creating an efficacious communication infrastructure.

  • Guarantee of Delivery

With XMPP, one can be double sure about the message delivery as it uses constant connectivity over TCP. It will hardly miss any XML stanza delivery, no matter how small it is.

  • Support by most of the Standard Programming Languages

Adoption at a large scale and huge global demand resulted in support for various languages. XMPP libraries are available in many leading languages like Perl, C++, C#, Java, Python, and many more. You name it and the XMPP library is most likely to be compatible with that language. This allowed developers to work in a compatible and preferred ecosystem.

  • Decentralized

XMPP is decentralized and permits multiple implementations. There is a restriction in server and library setup. Everyone can go with it. This grants more freedom and creates space for flexibility.

  • Higher Security

Boosted security is an added advantage of XMPP. While setting-up distinct XMPP servers, developers can choose encryption, security protocols, and access preferences as per the choice. Security is in full control resulting in fewer cyber-attacks and better peace of mind.

  • Uninterrupted Transmission of Data

Performance can be maintained easily as if one XMPP server is affected or is offline, regardless of the reasons, only corresponding users will be impacted. Rest will continue enjoying uninterrupted communication and data transmission. This has made achieving 100% operational continuity possible.

  • Server-to-Server Transfers

Server federation is an optional choice. Because of this, developers have the freedom to close the server-to-server for security reasons while assigning servers a specific task.

  • Compatibility

One major client-side advantage of XMPP is an abundance of clients. There is no dearth of XMPP clients. Regardless of the device type, you’ll find an XMPP client. It goes an extra mile for Windows and Unix systems by offering a command line. Also, one user can be signed up via different devices resulting in better accessibility.

The Crux

Paramount for constructing applications adept in real-time communication, XMPP (Extensible Messaging & Presence Protocol) is an utterly extendable protocol. Read the above article and find out other particulars about this inventive protocol. We have tried covering it comprehensively.

Originally published at https://www.wallarm.com.



Ivan Novikov

CEO at Wallarm. Application security platform to prevent threats and discover vulnerabilities in a real-time.