Cannot trace error in python pcapy wrapper

the answer is pretty simple:
p.next() will throw on timeout
your timeout is 100ms (last parameter of open_live)

so your except should handle the timeout case and you may want to increase the timeout time or set it to 0 for infinite

edit:
you simply expected socket.timeout but PcapError is thrown instead. socket.timeout is the exception thrown by the socket code in the python lib so it is python specific. It is getting wrapped up (maybe just with new versions of pcapy) or it jsut stands for a different kind of timeout (TCP socket related)
see example pcapy code: example

pcapy doesn't use Python socket module. It won't raise socket.timeout which is raised if timeout has been enabled by previous socket.settimeout call. socket.settimeout is used to set a socket into blocking, non-blocking or timeout state.

In pcapy, the timeout argument of open_live is passed to poll syscall at least in Linux, should differ by OS where poll is not available.

Reader.next call raises PcapError if there's no packet to return because it hasn't captured any packets yet. It's not an error, just an indication like StopIteration. It can be ignored and Reader.next has to be called again.

Reader.loop won't return until it has at least one packet to return or an error occurs.

The following code captures 10 packets and exits.

from pcapy import open_live, findalldevs, PcapErrorp = open_live("eth0", 1024, False, 100)dumper = p.dump_open("test.pcap")devices = findalldevs()print dumper, devicescount=0while True:    try:        packet = p.next()    except PcapError:        continue    else:        print packet        count += 1        if count == 10:            break