How to choose your inputs and outputs SRT type?

Link offers two input modes:

Listener (aka server mode): this is the default mode, where Link will act as a SRT server and listen for incoming connections from your SRT clients.
Caller (aka client mode), where Link will act as a SRT client and will initiate the connection to your SRT server.

You may wonder what are the differences between these two modes and why you should choose one or the other. Both modes have their pros and cons. Let's find out!

Link lets you choose the SRT type independently for each input and for each of its output, after their creation.

Listener Mode

Quortex Link input - SRT Listener configuration

The key advantage of the listener mode is that your streams should natively be able to traverse firewalls located between your SRT clients and Link, as these clients will initiate an outbound connection through the firewall towards Link. Enterprise firewall usually accept outbound connection on any protocol and to any IP:Port and the SRT connection should not be blocked.

Your IT may have blocked UDP outbound connection on some ports an/or some protocols. Please refer to your IT admin in such a case.

UDP hole punching, which is widely deployed in any firewall, will then be leveraged in the firewall so that the traffic coming from Link to your client can traverse this firewall.

One disadvantage of the listener mode is that Link will allocate a dedicated "IP:Port" to listen for incoming connections. This "IP:Port" can't be known ahead of time and is fully dynamic. Consequently, you need to create your input or output to be able to configure your SRT equipment (sender or receiver).

When using SRT in Listener mode for egress, only one SRT caller can connect per output. Multiple simultaneous callers require multiple SRT outputs (one per caller).

Link can automatically generate a random passphrase for securing the transmission. The passphrase can be found after the wizard step, by clicking on a given input.

In case you want to further increase the security, you can allow only a specific CIDR to establish a connection to Link. This can be done when you create your new input, or after by editing a given input.

Caller Mode

Quortex Link input - SRT caller configuration

When acting in caller (client) mode, you can make connections to any server to join streams. This can have advantages as you don't have to retrieve dynamic "IP:Port" information from Link to establish a connection.

In this mode, Link will initiate the connection to your SRT servers. In the case where these servers are located behind an enterprise firewall, you will need to check with your IT so they specifically open the UDP traffic coming from Link IP.

This IP is available after the wizard, when clicking on the input or output details.

Updated on: 13/08/2026

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