This topic provides an overview of listeners. After you create a Network Load Balancer (NLB) instance, you must configure one or more listeners for the NLB instance. An NLB listener is used to listen for connection requests and forward requests to backend servers based on a scheduling algorithm.
For more information, see Add a TCP listener.
Suitable for scenarios in which real-time transmission outweighs reliability, such as video conferencing and real-time quote services.
For more information, see Add a UDP listener.
NLB can forward encrypted TCP requests. You can use SSL over TCP in scenarios that require TCP while ensuring high security, such as large-scale TLS offloading.
For more information, see Create a listener that uses SSL over TCP.
|Listening ports (frontend ports)||Used by NLB to receive and forward requests to backend servers.||For each NLB instance:
|Service ports (backend ports)||Used by backend servers to receive requests.
An NLB instance can forward requests from a listening port to multiple backend ports that are used by different backend servers of the NLB instance.
|For each NLB instance:
You can associate a backend port with listeners that use different protocols. For example, you can associate a backend port with a listener that listens for TCP requests on port 80 and a listener that listens for TCP requests secured with SSL on port 81.