B4J Question Wait For doesn't return/resume if exception is thrown

[miker2069]

I was experiencing an issue with using wait for on a simple socket based connection. For example:

    Dim sock As Socket
    Dim Successful As Boolean
    '<----this IP doesn't exist or isn't listening on specified port so connect exception will be thrown
    Dim txtip As String = "10.0.0.23"
 
    sock.Initialize("sock")
    Log("Connect attempt")
    sock.Connect(txtip, 51042, 10000)
    'connect to nodemcu
    Wait For (Successful) sock_Connected (Successful As Boolean)
    Log("Returned from connection attempt")

I noticed that if I "wait for" sock_Connected and there's an exception thrown, the wait for never resumes. Now if instead use an independent event handler like so...

Sub sock_Connected (Successful As Boolean)

    Log("Connected Status:" & Successful)
    If Successful = False Then
        Log(LastException) 
    else
        Log("Successfully connected...")
    End If
End Sub

I can check the Successful result and if false check for the last exception. I was thinking I should be able to do all that after the wait for. So I am assuming if an exception occurs while waiting for an event, that wait for will sit there forever. Is this correct behavior? I thought an example of wait for in B4A with SQL that seems to demonstrate that it would gracefully return and possibly check the LastException.

To add to the discussion, I tried putting try/catch blocks around the wait for line and that didn't help - only way it works is to use a discrete sock_connected event handler routine.

For now I can re-arrange my code to work like I need it to - just looking for some clarity.

thanks!

 

[miker2069]

Looks like I had an error ( couldn't delete thread so I will post this addendum):

I changed the line:

  Wait For (Successful) sock_Connected (Successful As Boolean)

to:

  Wait For sock_Connected (Successful As Boolean)

And it works as expected - I can check the value of Successful and then dump lastexception. I was under the impression you had to parameterize the event args. Anyway sorry for the confusion.

 

[Erel]

The parameter inside the optional first parenthesis is the sender filter. It must match the Sender value for the event to be intercepted.

In your case the correct signature is:

Wait For (sock) sock_Connected (Successful As Boolean)

As a general rule it is better to use the sender filter when possible. It allows multiple resumable subs to wait for event with the same signature.