Below is an example showing how to use PyZMQ with Avahi for Zeroconf. The example is loosely based on the Python examples on avahi.org:
The example is unfinished and needs cleaning up, but I'm posting it here as requested by Brian:
#!/usr/bin/env python
# This is an example Avahi (zeroconf) extension for pyzmq.
# FIXME: This hasn't seen much love lately and really needs some
# move work. zmqconf could subclass pyzmq so that bind announces
# the service and connect discovers the service - using names
# instead of connection strings (eg. "tcp://192.168.0.1:5555").
# Copyright (C) 2010 David Robinson <[email protected]>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
import dbus
import gobject
import avahi # ey, provided by dbus-ui-tools package on Fedora?!
from dbus import DBusException
from dbus.mainloop.glib import DBusGMainLoop
from threading import Thread
MAX_RENAMES = 12
class zmqconf:
def __init__(self, domain='', host=''):
self.domain = domain
self.host = host
self.rename_count = MAX_RENAMES
self._services = []
self.group = None
DBusGMainLoop(set_as_default=True)
gobject.threads_init()
dbus.mainloop.glib.threads_init()
self.main_loop = gobject.MainLoop()
self.bus = dbus.SystemBus()
self.server = dbus.Interface(self.bus.get_object(avahi.DBUS_NAME, avahi.DBUS_PATH_SERVER), avahi.DBUS_INTERFACE_SERVER)
self.server.connect_to_signal("StateChanged", self._server_state_changed)
self._server_state_changed(self.server.GetState())
t = Thread(target=self.main_loop.run)
t.setDaemon(True)
t.start()
def browse_services(self, type, domain=''):
sbrowser = dbus.Interface(
self.bus.get_object(
avahi.DBUS_NAME,
self.server.ServiceBrowserNew(
avahi.IF_UNSPEC,
avahi.PROTO_UNSPEC,
type, domain,
dbus.UInt32(0))
),
avahi.DBUS_INTERFACE_SERVICE_BROWSER)
sbrowser.connect_to_signal("ItemNew", self._myhandler)
def close(self):
"""Close the socket.
This can be called to close the socket by hand. If this is not
called, the socket will automatically be closed when it is
garbage collected.
"""
# We can overwrite closing here
pass
def bind(self, addr):
"""Bind the socket to an address.
This causes the socket to listen on a network port. Sockets on the
other side of this connection will use :meth:`Socket.connect` to
connect to this socket.
Parameters
----------
addr : str
The address string. This has the form 'protocol://interface:port',
for example 'tcp://127.0.0.1:555'. Protocols supported are
tcp, upd, pgm, iproc and ipc.
"""
# Zeroconf doesn't makes sense for some transports
if addr[:3].lower() == 'ipc':
raise Exception("Cannot use Zeroconf with IPC")
elif addr[:5].lower() == 'inproc':
raise Exception("Cannot use Zeroconf with inproc")
# bind to the socket
#port = addr[addr.rindex(':') + 1:]
#proto = addr[:addr.index(':')]
# if the bind was successful (it'll raise an exception if not) publish details
proto, host, port = addr.split(':')
self.add_service("Example Service", "_example._tcp", 5555, "somethingcrazy")
#self.add_service("Example", proto, int(port), addr)
def _service_resolved(self, *args):
print 'service resolved'
print 'name:', args[2]
print 'address:', args[7]
print 'port:', args[8]
def _print_error(self, *args):
print args[0]
def _myhandler(self, interface, protocol, name, stype, domain, flags):
print "Found service '%s' type '%s' domain '%s' " % (name, stype, domain)
if flags & avahi.LOOKUP_RESULT_LOCAL:
# local service, skip
pass
self.server.ResolveService(interface, protocol, name, stype,
domain, avahi.PROTO_UNSPEC, dbus.UInt32(0),
reply_handler=self._service_resolved, error_handler=self._print_error)
def _add_services(self):
for service in self._services:
name, type, port, txt = service
self.add_service(name, type, port, txt)
def add_service(self, name, proto, port, txt):
print "Adding service '%s' of type '%s' ..." % (name, proto)
if self.group is None:
#self.bus = dbus.SystemBus()
#ob = self.bus.get_object(avahi.DBUS_NAME, avahi.DBUS_PATH_SERVER)
#self.server = dbus.Interface(ob, avahi.DBUS_INTERFACE_SERVER)
#eg = self.server.EntryGroupNew()
#ob = self.bus.get_object(avahi.DBUS_NAME, eg)
#self.group = dbus.Interface(ob, avahi.DBUS_INTERFACE_ENTRY_GROUP)
self.group = dbus.Interface(self.bus.get_object(avahi.DBUS_NAME, self.server.EntryGroupNew()), avahi.DBUS_INTERFACE_ENTRY_GROUP)
self.group.connect_to_signal('StateChanged', self._entry_group_state_changed)
self.group.AddService(
avahi.IF_UNSPEC, # interface
avahi.PROTO_UNSPEC, # protocol
dbus.UInt32(0), # flags
name, proto,
self.domain, self.host,
dbus.UInt16(port),
avahi.string_array_to_txt_array(txt))
self.group.Commit()
self._services.append((name, proto, port, txt))
def remove_services(self):
#global group
if not self.group is None:
self.group.Reset()
self._services = []
def _server_state_changed(self, state):
if state == avahi.SERVER_COLLISION:
print "WARNING: Server name collision"
self.remove_services()
elif state == avahi.SERVER_RUNNING:
self._add_services()
def _entry_group_state_changed(self, state, error):
if state == avahi.ENTRY_GROUP_ESTABLISHED:
print "Service established."
elif state == avahi.ENTRY_GROUP_COLLISION:
self.rename_count -= 1
if self.rename_count > 0:
self.name = server.GetAlternativeServiceName(self.name)
print "WARNING: Service name collision, changing name to '%s' ..." % self.name
self.remove_services()
self._add_services()
else:
print "ERROR: No suitable service name found after retrying, exiting."
self.main_loop.quit()
elif state == avahi.ENTRY_GROUP_FAILURE:
print "Error in group state changed", error
self.main_loop.quit()
return
if __name__ == "__main__":
# Publish a service
#context = zmq.Context(1, 1)
s = zmqconf()
address = "tcp://lo:5555"
#s.bind(address)
s.add_service("Example Service", "_example._tcp", 5555, "somethingcrazy")
raw_input("Press any key to exit")
# Discover services
#context = zmq.Context(1, 1)
#s = zmqconf()
#s.browse_services("_example._tcp")
#raw_input("Press any key to exit")
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