Small socket problem

John O'Hagan research at johnohagan.com
Mon Feb 9 10:43:36 CET 2009


Hi, 

I'm using the socket module (python 2.5) like this (where 'options' refers to 
an optparse object) to connect to the Fluidsynth program:

            host = "localhost"
            port = 9800
            fluid = socket(AF_INET, SOCK_STREAM)
            try:
                fluid.connect((host, port))  #Connect if fluidsynth is running
            except BaseException:
                print "Connecting to fluidsynth..." #Or start fluidsynth
                soundfont =  options.soundfont
                driver = options.driver
                Popen(["fluidsynth", "-i", "-s", "-g", "0.5",
                "-C", "1",  "-R", "1", "-l", "-a", driver, "-j", soundfont])
                timeout = 50
                while 1:
                    timeout -= 1
                    if timeout == 0:
                        print "Problem with fluidsynth: switching to synth."
                        play_method = "synth"
                        break
                    try:
                        fluid.connect((host, port))
                    except BaseException:
                        sleep(0.05)
                        continue
                    else:
                        break

(I'm using BaseException because I haven't been able to discover what 
exception class[es] socket uses).

The problem is that this fails to connect ( the error is "111: Connection 
refused") the first time I run it after booting if fluidsynth is not already 
running, no matter how long the timeout is; after Ctrl-C'ing out of the 
program, all subsequent attempts succeed. Note that fluidsynth need not be 
running for a success to occur. 

I've also tried it without the while loop, simply sleeping for a few seconds 
to give fluidsynth time to start (not a preferred approach as I want a short 
startup), but the same thing happens.

I am a long way from being a networking guru and am at a loss as to how to 
debug this. Maybe someone can point out some flaw in my use of socket.

Thanks,

John O'Hagan



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