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This is a sequel to my previous article on SMPP Library. Here are additional free and open source solutions.
smppapi
smppapi is an Java implementation of the Short Message Peer to Peer (SMPP) protocol. SMPP is used by applications to communicate with Service Centres to send and receive short messages to & from mobile devices.
The current implementation […]

OpenBTS is an open-source Unix application that uses the Universal Software Radio Peripheral (USRP) to present a GSM air interface ("Um") to standard GSM handset and uses the Asterisk software PBX to connect calls. The combination of the ubiquitous GSM air interface with VoIP backhaul could form the basis of a new type of cellular […]

The GNU Gatekeeper (GnuGk) is a full featured H.323 gatekeeper, available freely under GPL license. It forms the basis for a free IP telephony system (VOIP).
It is being used commercially by many organizations to provide VOIP services.

Executables for Linux, Windows, MacOS X, Solaris, FreeBSD, OpenBSD and NetBSD
can be run as a Windows service
accounting and call […]

Parlay X is set of Web service APIs for the telephone network (fixed and mobile.)
It enables software developers to use the capabilities of a underlying network. The APIs are deliberately high level abstractions and designed to be simple to use. An application developer can, for example, invoke a single Web Service request to get the […]

Kannel is an open source SMS and WAP gateway. It is developed on Linux using C but should be able to run on Unix like systems. For Windows, you will need the Cygwin to compile it.
For SMS services,

Work as both Pull and Push gateway
Can handle 7-bit, 8-bit and Unicode data
Delivery reports
Can handle hundreds of messages […]

Mbuni is a fully-fledged Free/Open Source Multimedia Messaging Service (MMS) gateway. It includes both core network MMS switching (i.e. MMSC) capabilities as well as messaging gateway (i.e. MMSC infrastructure integration) features, and is suitable for operators and MMS VAS providers.
Mbuni implements all major MMS interfaces, including phone-to-phone (so-called MM1 interface), phone-to-email (MM3), inter-MMSC (MM4) and […]

Have you ever noticed or aware of the ‘+’ sign that is prefixed in the phone number that we dial or store in the address book in our mobile phone? What is the significance of putting a ‘+’ sign in front?
All the telephone numbers we dial follow certain format known as E.164 addressing format – […]

Frankly speaking I haven’t tested it yet. I was browsing through the projects by JBoss, and discovered Mobicents.
Telco is one area that I am always interested in, as most of my projects are telco related. It is interested to see a open source project like Mobicents.
According to JBoss, Mobicents is a highly scalable event-driven […]