Socket: Failed to read side-channel request

[Thomas Küstermann]

Hello!

I am currently in the process of replacing our plain old cups (version 1.1.x) with newest available one (version 1.3.7 at the moment I write this message).

We're using the socket backend to print. Now, we've got some problems in printing with the new version. I try to explain:

I want to print a document (PDF) on a HP Laserjet 4350/4050/2430, the first pages were printed out and suddenly the printer stops printing with the following 'error' message:

'Data recieved'
'Press <checkmark> to print last page'

If I press <checkmark> or wait until a timeout is received, the printer continues printing, but it prints out plain PostScript.

I've logged the output of the socket backend and received the following one:

<log>
INFO: Attempting to connect to host <printer> on port 9100
STATE: +connecting-to-device
STATE: -connecting-to-device
INFO: Connected to <printer>...
DEBUG: Connected to <printer>:9100 (IPv4)...
PAGE: 1 1
DEBUG: backendRunLoop(print_fd=3, device_fd=4, use_bc=1, side_cb=0x401862)
INFO: Printer is now on-line.
DEBUG: Read 8192 bytes of print data...
DEBUG: Wrote 8192 bytes of print data...
. 
. 
. 
WARNING: Failed to read side-channel request!
// some time later :
DEBUG: Read 8192 bytes of print data...
DEBUG: Wrote 8192 bytes of print data...
. 
. 
. 
INFO: Sent print file, 5160398 bytes...
INFO: Print file sent, waiting for printer to finish...
INFO: Ready to print.
</log>

The problem is reproducible, but it seems to NOT depend on:
- document size
- number of pages

What I can say about the documents:
- they seem to be complete (correct head and tail)
- they can be rendered completely with ghostview ('gv <file>')

If I try to print the document on the old cups, it succeeds. PPD files are the same and original ones from HP.

What maybe the next steps to find the reason for problem, or maybe to resolve? Thanks in advance for each hint.

- Thomas