How To | Verify Closed Captioning is coming from the playback server

Learn how to check if your playback server is providing accurate closed captioning.

Updated at June 8th, 2023


A good test to see if a server and the network switch will support captioning is to telnet to the server on port 4170 (the port reserved for the auxiliary content synchronization protocol). If you are using Putty as the telnet client, you should select "Raw" as the connection type.

If the connection is refused, captioning will not work. Run a software update on the server if needed and confirm that the server CCAP settings are configured properly.

If the connection is accepted, you will see some text and garbage output, then the connection disconnected. Captioning setup on the server is correct.