# Calling APIs

### PortSIP VoIP SDK

[PortSIP VoIP SDK](https://www.portsip.com/portsip-voip-sdk/) is a modern, production-ready SIP client framework designed for building high-performance audio and video calling applications. It supports all major operating systems, enabling rapid time-to-market for applications on:

* iOS
* Android
* macOS
* Windows
* WebRTC (Browsers)

This broad platform coverage allows developers and service providers to deliver consistent, high-quality communication experiences across desktop, mobile, and web environments.

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### Unified Communications Capabilities

The PortSIP VoIP SDK enables the development of full-featured Unified Communications applications, including:

* Audio and video calling
* Instant messaging (IM)
* Screen sharing
* File transfer
* Picture messaging
* Voice and video messages

By providing these capabilities out of the box, the SDK significantly reduces development complexity and accelerates the delivery of enterprise-grade UC solutions.

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### Trusted by Industry Leaders

The PortSIP VoIP SDK is trusted and used by many well-known global enterprises, including (but not limited to):

* Siemens
* T-Mobile
* Telstra
* Netflix
* Qualcomm
* HPE
* Nextiva
* Keysight
* Philips
* Panasonic
* Fujitsu
* Dialogic

These organizations rely on PortSIP to power mission-critical communication workflows at scale.

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### Included with PortSIP PBX — No Extra Cost

When you purchase a **PortSIP PBX** license, the **PortSIP VoIP SDK is included at no additional cost**.

This provides a true **all-in-one Unified Communications platform**, allowing you to:

* Build custom client applications
* Deploy UCaaS, CCaaS, or CPaaS solutions
* Reduce licensing complexity and overall cost
* Achieve the shortest possible time-to-market

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### Obtain the SDK

You can download the PortSIP VoIP SDK directly from the [PortSIP website](https://www.portsip.com).\
The SDK package includes **ready-to-run sample projects** for multiple operating systems, making it easy to explore features and start development immediately.

For technical support or integration assistance, you can [submit a support ticket](https://portsip.atlassian.net/servicedesk/customer/portals) directly to PortSIP.