SEMS is a media and application server for SIP based VoIP services. It shows good performance doing basic services like announcements and conference for combination with external application servers. Thanks to its easy-to-use and flexible application development framework and back-to-back user agent support, application logic and media serving can be combined in the same process. Basic applications like announcement, pre-call announcement, RBT, conference, voicemail, mailbox, and lots of example applications are available. Scripting can be done in Python and a simple state machine description language. Support All commonly used free codecs (including g711, gsm, iLBC, speex, adpcm, and l16) are supported. Other features include wideband, ZRTP encryption, a SIP registrar client, an XMLRPC server/client, and a DIAMETER client.
Zato is an Enterprise Service Bus (ESB) and app server written by pragmatists for pragmatists. It provides an HA load-balancer, hot-deployment, and hot-reconfiguration almost everywhere (forget server restarts). It has a browser-based GUI, CLI, and API (forget XML configuration). It supports many protocols, industry standards, and data formats, including HTTP, JSON, SOAP, REST, AMQP, JMS WebSphere MQ, ZeroMQ, Redis, SQL, and FTP.