Pidgin is a free and open-source multi-platform instant messaging client, based on a library named libpurple that has support for many instant messaging protocols, allowing the user to simultaneously log in to various services from a single application, with a single interface for both popular and obsolete protocols, thus avoiding the hassle of having to deal with new software for each device and protocol.
Skype is a proprietary telecommunications application operated by Skype Technologies, a division of Microsoft, best known for VoIP-based videotelephony, videoconferencing and voice calls. It also has instant messaging, file transfer, debit-based calls to landline and mobile telephones, and other features. It is available on various desktop, mobile, and video game console platforms.
OpenVPN is a virtual private network (VPN) system that implements techniques to create secure point-to-point or site-to-site connections in routed or bridged configurations and remote access facilities. It implements both client and server applications.
Asterisk is a software implementation of a private branch exchange (PBX). In conjunction with suitable telephony hardware interfaces and network applications, Asterisk is used to establish and control telephone calls between telecommunication endpoints such as customary telephone sets, destinations on the public switched telephone network (PSTN) and devices or services on voice over Internet Protocol (VoIP) networks. Its name comes from the asterisk (*) symbol for a signal used in dual-tone multi-frequency (DTMF) dialing.
The landscape for instant messaging involves cross-platform instant messaging clients that can handle one or multiple protocols. Clients that use the same protocol can typically federate and talk to one another. The following table compares general and technical information for cross-platform instant messaging clients in active development, each of which have their own article that provide further information.
Google Talk was an instant messaging service that provided both text and voice communication. The instant messaging service was variously referred to colloquially as Gchat, Gtalk, or Gmessage among its users.
Skype for Business Server is real-time communications server software that provides the infrastructure for enterprise instant messaging, presence, VoIP, ad hoc and structured conferences and PSTN connectivity through a third-party gateway or SIP trunk. These features are available within an organization, between organizations and with external users on the public internet or standard phones.
SipXecs is a free software enterprise communications system. It was initially developed by Pingtel Corporation in 2003 as a voice over IP telephony server located in Boston, MA. The server was later extended with additional collaboration capabilities as part of the SIPfoundry project. Since its extension, sipXecs now acts as a software implementation of the Session Initiation Protocol (SIP), making it a full IP-based communications system.
Marratech was a Swedish company that made software for e-meetings. It was acquired by Google in 2007.
QuteCom was a free-software SIP-compliant VoIP client developed by the QuteCom community under the GPL-2.0-or-later license. It allows users to speak to other users of SIP-compliant VoIP software at no cost. It also allows users to call landlines and cell phones, send SMS and make video calls. None of these functions are tied to a particular provider, allowing users to choose among any SIP provider.
Zfone is software for secure voice communication over the Internet (VoIP), using the ZRTP protocol. It is created by Phil Zimmermann, the creator of the PGP encryption software. Zfone works on top of existing SIP- and RTP-programs, but should work with any SIP- and RTP-compliant VoIP-program.
This is a comparison of voice over IP (VoIP) software used to conduct telephone-like voice conversations across Internet Protocol (IP) based networks. For residential markets, voice over IP phone service is often cheaper than traditional public switched telephone network (PSTN) service and can remove geographic restrictions to telephone numbers, e.g., have a PSTN phone number in a New York area code ring in Tokyo.
FreeSWITCH is a free and open-source telephony software for real-time communication protocols using audio, video, text and other forms of media. The software has applications in WebRTC, voice over Internet Protocol (VoIP), video transcoding, Multipoint Control Unit (MCU) functionality and supports Session Initiation Protocol (SIP) features.
Jitsi is a collection of free and open-source multiplatform voice (VoIP), video conferencing and instant messaging applications for the Web platform, Windows, Linux, macOS, iOS and Android. The Jitsi project began with the Jitsi Desktop. With the growth of WebRTC, the project team focus shifted to the Jitsi Videobridge for allowing web-based multi-party video calling. Later the team added Jitsi Meet, a full video conferencing application that includes web, Android, and iOS clients. Jitsi also operates meet.jit.si, a version of Jitsi Meet hosted by Jitsi for free community use. Other projects include: Jigasi, lib-jitsi-meet, Jidesha, and Jitsi.
Linphone is a free voice over IP softphone, SIP client and service. It may be used for audio and video direct calls and calls through any VoIP softswitch or IP-PBX. Linphone also provides the possibility to exchange instant messages. It has a simple multilanguage interface based on Qt for GUI and can also be run as a console-mode application on Linux.
Empathy was an instant messaging (IM) and voice over IP (VoIP) client which supported text, voice, video, file transfers, and inter-application communication over various IM communication protocols.
In the field of VoIP networking, the Open Phone Abstraction Library (OPAL) continues the open-source openh323 project to support a wide range of commonly used protocols used to send voice, video and fax data over IP networks rather than being tied to the H.323 protocol. Initially, from 2007, OPAL supported the H.323 and Session Initiation Protocol (SIP) protocols, but it has grown to include Asterisk IAX2.
Jami is a SIP-compatible distributed peer-to-peer softphone and SIP-based instant messenger for Linux, Microsoft Windows, macOS, iOS, and Android. Jami was developed and maintained by the Canadian company Savoir-faire Linux, and with the help of a global community of users and contributors, Jami positions itself as a potential free Skype replacement.
GNU SIP Witch is free SIP server software with peer-to-peer capabilities from the GNU Project. It is the GNU implementation of the Session Initiation Protocol (SIP), which is used for the routing of calls.
