Avoiding SMS vendor lock-in with SMPP

There is increasing demand for SMS notifications about monitoring alerts, trading notifications, flight delays and other events. Various companies are offering SMS transmission services to meet this demand and many of them aggressively pushing their own proprietary interfaces to the SMS world rather than using the more open and widely supported SMPP.

There is good reason for this: if users write lots of of scripts to access the REST API of an SMS service, the users won't be able to change their service provider without having to change all their code. Well, that is good if you are an SMPP vendor but not if you are their customer. If an SMS gateway company goes out of business or has a system meltdown, the customers linked to their REST API will have a much bigger effort to migrate to a new provider than those using SMPP.

The HTTP REST APIs offered by many vendors hide some details of the SMS protocol and payload. At first glance, this may feel easier. In fact, this leads to unpredictable results when delivering messages to users in different countries and different character sets/languages. It is better to start with SMPP from the beginning and avoid discovering those pitfalls later. The SMS Router free/open source software project helps overcome the SMPP learning curve by using APIs you are already familiar with.

More troublesome for large organizations, some of the REST APIs offered by SMS gateways want to make callbacks to your own servers: this means your servers need public IP addresses accessible from the Internet. In some organizations that can take months to organize. SMPP works over one or more outgoing TCP connections initiated from your own server(s) and doesn't require any callback connections from the SMPP gateway.

SMS Router lets SMS users have the best of both worlds: the flexibility of linking to any provider who supports SMPP and the convenience of putting messages into the system using any of the transports supported by an Apache Camel component. Popular examples include camel-jms (JMS) for Java and J2EE users, STOMP for scripting languages, camel-mail (SMTP and IMAP) for email integration and camel-sip (SIP) or camel-xmpp (XMPP) for chat/instant messaging systems. If you really want to, you can also create your own in-house HTTP REST API too using camel-restlet for internal applications. In all these cases, SMS Router always uses standard SMPP to reach any gateway of your choice.

Architecture overview

SMS Router is based on Apache Camel. Multiple instances can be operated in parallel for clustering, load balancing and high availability. It can be monitored using JMX solutions such as JMXetric.

The SMPP support is based on the camel-smpp component which is in turn based on the jSMPP library, which comprehensively implements the SMPP protocol in Java. camel-smpp can be used with minimal configuration but for those who want to, many SMPP features can be tweaked on a per-message basis using various headers.

The SMPP gateway settings can be configured and changed at will using the sms-router.properties file. The process doesn't require any other files or databases at runtime.

The SMS Router is ready-to-run with one queue for sending messages and another queue for incoming messages. The routing logic can be customized by editing the RouteBuilder class to use other Camel components or any of Camel's wide range of functions for inspecting, modifying and routing messages. For example, you can extend it to failover to multiple SMPP gateways using Camel's load-balancer pattern.

SMS Router based projects are already used successfully in production, for example, the user registration mechanism for the Lumicall secure VoIP app for Android.

Getting started

See the README for instructions. Feel free to ask questions about this project on the Camel users mailing list.


SMS is not considered secure, the SMS Router developers and telecommunications industry experts discourage the use of this technology for two-factor authentication. Please see the longer disclaimer in the README file and my earlier blog about SMS logins: an illusion of security. The bottom line: if your application is important enough to need two-factor authentication, do it correctly using smart cards or tokens. There are many popular free software projects based on these full cryptographic solutions, for example, the oath-toolkit and dynalogin.