# 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.

***

### 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.

***

### 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.

***

### 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

***

### 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.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://support.portsip.com/development-portsip/calling-apis.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.