Backchannel usage

[Michael Sweet]

Josh Mathis wrote:
> I am trying to add some simple status support into my filter. Before the
> print data of a job is sent, I attempt to send a status request (escape
> command) and then read a two-byte response. However, the function
> always fails (return -1).
> 
> To do a basic test, I changed the filter to only send a 3-byte status 
> request with printf, just like normal print data, then read the 2-byte 
> response with cupsBackChannelRead, then exit the job. However, the read 
> always times out and returns -1. I have confirmed that the printer is 
> receiving the status request, but it seems that the backend is not 
> picking up the response.
> 
> Here is what I am doing:
> 
> char backbuffer[1024]; //buffer for returned data
> printf("\x1b\x05\x06"); //send status request

Add a fflush(stdout) call here, otherwise your printf output will
not actually get sent to the printer... :)

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______________________________________________________________________
Michael Sweet, Easy Software Products           mike at easysw dot com
Internet Printing and Document Software          http://www.easysw.com