Simplified Streaming: Wowza Streaming Engine 4.9.4 Introduces SRT Listener Mode

Taking Low-Latency Streaming to the Next Level

2025 is shaping up to be the year of simplified, secure streaming solutions. At Wowza, we’re excited to announce that with our latest Wowza Streaming Engine 4.9.4 release, we’ve significantly improved our SRT implementation by introducing listener mode – a game-changer for broadcasters looking to streamline their video contribution workflows.

Let’s dig in.

SRT: A Quick Refresher

For those who might need a refresher, SRT (Secure Reliable Transport) is an open-source protocol designed by Haivision and championed by the SRT Alliance. It serves as an excellent RTMP alternative, specifically created to transport low-latency streams over challenging network conditions.

What makes SRT special? By combining UDP’s speed with TCP’s error-correction capabilities, SRT delivers reliable, low-latency streams regardless of network quality. This hybrid approach means broadcasters benefit from:

• Packet loss recovery
• Simplified firewall traversal
• End-to-end encryption capabilities
• Consistent performance even on unstable networks

The Power of Listener Mode

With traditional SRT implementations, managing multiple incoming streams required separate configuration files and unique ports for each stream – creating unnecessary complexity for broadcasters handling multiple sources.

Our new SRT listener mode fundamentally changes this approach. Are you looking for simplified multi-stream management?

How Listener Mode Works

In listener mode, the encoder “pushes” the stream to the server, similar to how RTMP-based encoders work. This means the encoder initiates the connection when it’s ready without requiring any action on the server side.

I’ve seen firsthand how this shift in connection approach dramatically reduces configuration overhead for our customers managing multiple incoming streams.

Listener Mode vs. Caller Mode: A Clear Comparison

Feature	Listener Mode	Caller Mode
Connection Initiation	Encoder/source initiates connection	Engine initiates connection to encoder/source
Port Requirements	Single UDP port for all SRT streams	Unique UDP port for each SRT stream
Configuration	Basic config and Live App setup for all streams	Requires Medicaster and Stream file setup for each steam, plus Live App setup
Networking	Easy firewall/NAT setup (single port)	More complex due to multiple UDP ports
Security	Supports passphrase per user in multitenant environments	Not supported
Stream Identification	StreamId support for authentication and identification	Not supported

Key Benefits That Matter to Broadcasters

Based on what we’ve seen in implementation, SRT listener mode delivers several critical advantages:

1. Dramatically Simplified Configuration

Ideal for scenarios where your Engine handles multiple sources or clients, listener mode requires WSE to listen on just one specific port – making configuration straightforward and intuitive.

2. Efficient Multiple Connection Support

Your WSE can now handle multiple incoming connections from different callers on the same port, eliminating the need to manage separate ports for each stream.

3. Firewall-Friendly Setup

Need to manage firewall or NAT settings? With listener mode, you’ll only need to configure a single port instead of managing separate ports for each source, stream, or client.

4. Enhanced Security Features

Security remains a top concern for broadcasters in 2025. Our listener mode implementation supports passphrases per user/stream, making it secure in multitenant environments. The StreamId support provides robust authentication and stream identification capabilities.

5. Built for Scalability

If you’re running media servers that need to handle multiple streams from various sources, listener mode provides a flexible and efficient way to manage, identify, and route streams in multi-stream or multi-tenant environments.

Getting Started with SRT Listener Mode

Setting up SRT listener mode requires a one-time configuration of Server.xml, VHost.xml, and Application.xml files. We’ve streamlined the process to make implementation as straightforward as possible.

For detailed implementation instructions, check out our comprehensive documentation:

• Ingest and publish an SRT stream with Wowza Streaming Engine
• Configure SRT listener mode
• Wowza Streaming Engine VHost.xml configuration reference

Conclusion

As streaming workflows continue to evolve in complexity, simplifying connection management while enhancing security becomes increasingly crucial. SRT listener mode represents our commitment to developing solutions that address real-world broadcaster challenges.

I predict we’ll see rapid adoption of this functionality, particularly among broadcasters managing multiple remote contribution points or operating in environments where network reliability is a concern.

We look forward to seeing how the new SRT listener mode impacts our customers’ operations.