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How does a SIP server work - VaxVoIP

SIP server - absolutely free

Unlock the power of SIP communication with our absolutely free SIP server! VaxVoIP offers a robust and feature-rich SIP server perfect for creating IP-PBX systems, auto-dialers, and call center solutions. Enjoy seamless integration with various SIP devices and experience unparalleled flexibility. Start building your SIP server today with VaxVoIP.

SIP servers enhance communication

They do this by managing and directing SIP-based communication sessions, such as VoIP calls, video conferences, and messaging. They handle call setup, routing, signaling, and termination, ensuring efficient and reliable connections. SIP servers also support advanced features like call forwarding, voicemail, presence information, and interoperability between different devices and networks, significantly improving the flexibility, scalability, and functionality of communication systems.

How does a SIP server work

In simple terms, a SIP server is like a smart switchboard operator for internet calls, making sure you can talk to the right person at the right time.

The 5 steps of how SIP server works

a. Registering:

When you want to make or receive calls, your device first tells the server, "I'm here and ready!" This is called registering.

b. Making a Call:

When you dial a number, your device sends a request to the server, saying, "I want to talk to this person."

c. Finding the Person:

The server checks where the person you're calling is registered. It finds their device and sends a message saying, "Someone wants to talk to you."

d. Establishing the Call:

If the person answers, the server helps connect your device to their device. Now, you can talk directly over the internet.

e. Ending the Call:

When the call is over, the server helps end the connection cleanly, making sure both sides know the call is finished.

Session initiation protocol

SIP is a communication protocol used to initiate, manage, and terminate real-time sessions involving voice, video, messaging, and other media. It simplifies setting up calls over the internet by handling the signaling and control required for these sessions.

SIP is essential for VoIP (Voice over Internet Protocol) and enables features like call forwarding, conferencing, and voicemail, making internet-based communication easy and efficient.

VoIP (Voice over Internet Protocol) is a technology that allows voice communication over the internet. SIP is a signaling protocol used within VoIP to initiate, manage, and terminate calls. Essentially, VoIP is the overall method of delivering voice communications, while SIP is a specific protocol used to set up and control these calls, as well as support other features like video and messaging.

SIP proxy server

The server enhances communication by supporting video calls, instant messaging, video conferencing, and telephony. It manages and directs SIP-based sessions, ensuring reliable connections and efficient call handling. This flexibility allows seamless integration with various devices and networks, making it an ideal solution for modern communication needs. Enjoy advanced features and robust performance with VaxVoIP.

What are SIP proxies

They act as intermediaries in a SIP network, making sure that calls and messages get to the right place efficiently and securely. A SIP proxy is like a middleman in the world of internet phone calls. It helps connect the calling and receiving devices by directing the call setup messages to the right place.

How do they work

Receiving Requests:

When you want to make a call, your device sends a SIP request to the SIP proxy. This request includes information about who you want to call.

Routing the Call:

The SIP proxy looks at the request and figures out where to send it next. It might send it directly to the recipient's device or to another SIP proxy closer to the recipient.

Forwarding Responses:

The recipient's device sends back a response, like "I'm ringing" or "I'm busy." The SIP proxy forwards this response back to your device so you know what's happening.

Helping with Call Setup:

If the call is accepted, the SIP proxy helps set up the direct communication path between your device and the recipient's device.


  1. Scalability:

    They can handle many calls at once, making it easier to manage large networks.

  2. Security:

    They can provide security features, like verifying the identity of users and encrypting messages.

  3. Load Balancing:

    They can distribute call traffic evenly across the network to prevent any single server from being overwhelmed.

  4. Failover:

    If one server goes down, the SIP proxy can route calls through another server, ensuring continuous service.

What is SIP trunking

SIP trunking is a technology that allows businesses to make and receive phone calls over the internet using the Session Initiation Protocol (SIP). Here's a simple explanation: Think of SIP trunking as a virtual phone line that uses the internet instead of traditional phone lines to connect calls. It's like replacing old phone cables with an internet connection for your phone system.

Contact VAXVOIP for a Free trial

Below is a list of our key services, each linked to a page where you can find more information and get started:

  • Web Phone SDK: Enables the development of web-based VoIP solutions, allowing calls directly from browsers.
  • SIP Phone SDK: Provides the tools needed to create custom SIP softphone applications for desktops and mobile devices.
  • SIP Recording SDK: Offers capabilities for recording VoIP calls, essential for quality assurance and compliance purposes.