Cannot extract WebSocket Sampler response and store as variable

Question

I am trying to test our API on WS using WebSocket Sampler(Maciej Zaleski)

I want to extract the response from the first API and store the matched pattern as variable, then pass it to the next request

But I failed and failed again on getting empty result

Answer 1

To extract by regular expression you need to find a group, Group is found using () which you are missing.

In your case use Regular Expression: FH(\d{5}-\d{7})

Also you need to provide Template,in your case for first group, use $1$