[PyQt] QTcpSocket connections

[Phil Thompson]

On Mon, 22 Jul 2013 16:31:55 +0200, Jorge Tornero - Listas
<jtorlistas at gmail.com> wrote:
> Hello everybody,
> 
> I'm trying to share a digital scale through the network, making it able 
> to receive tare/send weight commands.
> The scale is connected to a remote computer (a raspberry pi, by the way)

> with a serial converter an the raspi is executing remserial, thus makin 
> avalilable the serial port to the network through port 23000.
> 
> Because I am making my application with PyQt4, I have chosen to use 
> QTcpSocket to do the communications between the computers. It is pretty 
> easy and I am able to get what i want (sending command and receiving 
> weights) just by:
> 
> soc=QtNetwork.QTcpSocket()
> 
> 
> soc.connectToHost('174.33.22.11',23000)
> 
> soc.writeData('01ST@')
> print soc.readAll()
> soc.disconnectFromHost()
> 
> 
> And of course I get the weight and I am able to repeat the cycle 
> connect-poll-receive-disonnect
> 
> The problem is whe I put that into a function like:
> 
> def captura():
> 
>    soc=QtNetwork.QTcpSocket(app)
>    comandoCaptura=chr(6)+'01S@'+chr(13)
>    soc.connectToHost('172.23.2.25',23000)
>    soc.writeData(comandoCaptura)
>    a=soc.readAll()
>    print a
>    soc.disconnectFromHost()
>    return a
> 
> 
> Ther is no wai to make it works. I guess is a basic python issue, but 
> can anyone help?

QTcpSocket is asynchronous, so you need an event loop. After calling
connectToHost() you shouldn't try to read or write until the connected()
signal has been emitted.

Phil