What is VOIP Client (Softphone)? Features and Protocols

A VoIP Client, also known as a softphone, is a software application that simulates the work of a telephone and lets you make, receive and manage calls over the Internet. It is a piece of software which functions as a phone interface and can be installed on your computer or smartphone.

A softphone is a program, and so, it needs some additional hardware to support its functionalities. The VoIP Client makes use of the internet for sending voice information.


The calls can be done with the help of standard internet connection on your local network, wireless networking (WiFi) or cellular data network (3G/4G).

The VoIP Client is a feature-rich application with lots of benefits as well. So, let’s begin by knowing what constitutes a this softphone.

What are the parts of a softphone?

The softphone (or VoIP Client) consists of four essential parts. They are discussed below.

  • There is an interface which is the bridge for communication between the user and the device. It has control buttons for managing calls.

The interface provides a dial pad for dialing numbers and a keyboard for entering names of contacts and performing searches.

It deals with the audio input and output of the device for playing sounds and capturing audio during a call.

  • An engine for call processing is present. It also has modules in a communication API to place and receive calls in a specific protocol.
  • A set of codecs encode the voice data between analog (as we hear and speak naturally) and digital formats. It also compresses the data for easy transfer over the internet.
  • A contact list is also there to monitor and manage the numbers.

What is the VoIP service?

The VoIP client works with a VoIP service or SIP (Session Initiation Protocol) server for making calls. The VoIP service is a subscription you take from the VoIP service provider to make calls.

The calls are very cheap with VoIP and often free and unlimited if both the callers use the same VoIP service and VoIP client.

Most of the VoIP service providers allow free download and installation of their VoIP Client.

There are different types of VoIP services available, and you can choose the one you need as per your requirement. They are as follows

Residential VoIP services

This service replaces the traditional landline phones and instead, keeps the existing telephone together with a phone adapter. It is paid monthly and applies to businesses using IP phones.

No-monthly bill services

This service provides you with a one-time payable, special hardware. It facilitates unlimited calls.

Software-based services

You have to install a VoIP app on your device and register with this service (like in Skype). Then, you can use the app for making or receiving calls.

You can also use your prepaid credit card to make calls to landlines and mobiles.

The calls to people using the same service are free. The app is also sometimes offered for free with the VoIP service.

The software-based services which are meant for use on phones, tablets or other portable devices are called mobile VoIP services.

You need to install a VoIP on your device and use Wifi or 3G/4G connections in place of cellular calling minutes.

VoIP services for businesses

These are based around internal networks and IP PBXes. It also provides many business-related aspects and outsourcing for the VoIP system’s management.

The VoIP client (or softphone) has evolved rapidly with the advancement of the VoIP industry. Earlier, it was just a replica of the traditional phone over a screen. Now, it acts as the primary interface for communication apps.

It may differ based on its functionalities, purpose of use, sophistication and protocol complexity.

What are the features of VoIP client?

VoIP client has many features. It may be a simple software program or a complex application based on the functionality and purpose of use.

It may simply be softphone with dialing interface, contact memory, user ID and some other basic characteristics.

Or, it may be a complex application with additional functionalities, apart from call managing, like network statistics, QoS support, voice security, video conferencing, etc.

Some of the basic features of VoIP softphones are as follows:

  • Call forwarding, call transferring and call conferencing
  • Hold capabilities
  • Voicemail
  • Greetings capability
  • Text and video capabilities
  • Contact list or address book
  • Echo cancellation for improving the quality of sound

Softphone helps to save costs and is beneficial for green companies as it consumes less energy than phone and phone system hardware.

What is the protocol supported by VoIP softphone?

SIP (Session Initiation Protocol) is one of the strongest pillars of VoIP and the most widely used protocol in VoIP softphones.

It is designed to offer calling features of traditional telephone systems and provides the service to the machines having SIP compatible VoIP client installed and registered.

SIP is the protocol that states that either of the two ends of a conversation can initiate a transaction (conversation) and both the ends will have an end-to-end connection during the interaction.

The end-to-end connection breaks once the interaction finishes.

It is ubiquitous in corporate sectors and businesses where employees have the VoIP clients installed and registered on their computers, laptops or smartphones.

A SIP client intends to establish real-time communications (RTCs), and that’s why very popular for softphone functionality.

It may also provide video capabilities, chat, file transfer, and remote desktop access. SIP VoIP client is easy to configure as well as generic and not bound to any particular service.

Top business VoIP providers highly recommend SIP clients like 3CX, Bria, and SIPDroid.

SIP clients can be installed on your machine and set up for use by any service offering SIP compatibility. Then, you can make calls through it and pay the VoIP service provider.

Examples of SIP VoIP clients

X-Lite, MicroSIP, JitSi, Blink Pro, etc are some of the notable SIP VoIP clients.

Other Protocols supported by softphones

Some other protocols used by softphones are H.323, Media Gateway Control Protocol (MGCP), Cisco’s Skinny Client Control Protocol (SCCP) and IAX of Asterisk.

Who benefits from softphones?

A VoIP client (or softphone) has a range of features which are very beneficial for the users. It is well known for its scalability, mobility, cost-effectiveness, quick updates, and easy setups.

Different categories of users which can benefit from its use are as follows

VoIP Beginners

They explore the way how the service works. VoIP beginners download a softphone to make free computer-to-computer or computer-to-phone calls. They discover the functionality of the service in a cheap and fast way.

Heavy travelers

VoIP clients help heavy travelers to save the hassle and expenses of using a hotel telephone or roaming charges on a cell phone. They avoid the large bills by using a low-cost VoIP service with a VoIP softphone.


Telecommuters often need to work and communicate from locations outside their offices.

By registering the VoIP softphones with their office PBX (Private branch exchange) system, the telecommuters can conveniently make calls with the same features at the office.

Call center employees

Softphones are cheap and easy to upgrade. Call center employees save costs by implementing VoIP softphones instead of using desk phones.

Small businesses

Small business organizations incorporate VoIP softphones and save money by cutting ties with expensive traditional telephone companies. VoIP softphones do not require costly hardware for maintenance which is a bonus point.

Long distance callers

International and long distance call rates are reduced when VoIP softphone is used. It facilitates users to make convenient and cheap out-of-state/country calls.



So, we see that VoIP client (also called softphone) is a software program, installed on a user’s device (computer, laptop or smartphone) which aids in making and managing VoIP calls. It requires few additional hardware devices like microphone, headset, webcam for the user to communicate appropriately.

You will require a VoIP service provider to get the subscription for using the VoIP client to make calls. Mostly, Session Initiation Protocol (SIP) is the protocol implemented for VoIP clients, though there are other protocols available too.

VoIP client is rich with features like call managing, video capabilities, echo cancellation, voicemails, etc and is beneficial to users from small businesses to heavy travelers, call centers to telecommuters.

While talking about VoIP clients, the first and foremost example that anyone can think of is Skype’s software. It allows people to make voice and video calls globally, mostly for free.

Other notable examples of free VoIP softphones are CounterPath’s X-Lite, 3CX, PBX in a Flash, Firefly, Twinkle, etc. Examples of paid VoIP softphones include Bria 3, Eyebeam, Optima Dialer, JusTex, etc.


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