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"""Port forwarder with graceful exit.
Run the example as
python portforwarder.py :8080 gevent.org:80
Then direct your browser to http://localhost:8080 or do "telnet localhost 8080".
When the portforwarder receives TERM or INT signal (type Ctrl-C),
it closes the listening socket and waits for all existing
connections to finish. The existing connections will remain unaffected.
The program will exit once the last connection has been closed.
"""
import sys
import signal
import gevent
from gevent.server import StreamServer
from gevent.socket import create_connection, gethostbyname
class PortForwarder(StreamServer):
def __init__(self, listener, dest, **kwargs):
StreamServer.__init__(self, listener, **kwargs)
self.dest = dest
def handle(self, source, address):
log('%s:%s accepted', *address[:2])
try:
dest = create_connection(self.dest)
except IOError, ex:
log('%s:%s failed to connect to %s:%s: %s', address[0], address[1], self.dest[0], self.dest[1], ex)
return
gevent.spawn(forward, source, dest)
gevent.spawn(forward, dest, source)
# XXX only one spawn() is needed
def close(self):
if self.closed:
sys.exit('Multiple exit signals received - aborting.')
else:
log('Closing listener socket')
StreamServer.close(self)
def forward(source, dest):
source_address = '%s:%s' % source.getpeername()[:2]
dest_address = '%s:%s' % dest.getpeername()[:2]
try:
while True:
data = source.recv(1024)
log('%s->%s: %r', source_address, dest_address, data)
if not data:
break
dest.sendall(data)
finally:
source.close()
dest.close()
def parse_address(address):
try:
hostname, port = address.rsplit(':', 1)
port = int(port)
except ValueError:
sys.exit('Expected HOST:PORT: %r' % address)
return gethostbyname(hostname), port
def main():
args = sys.argv[1:]
if len(args) != 2:
sys.exit('Usage: %s source-address destination-address' % __file__)
source = args[0]
dest = parse_address(args[1])
server = PortForwarder(source, dest)
log('Starting port forwarder %s:%s -> %s:%s', *(server.address[:2] + dest))
gevent.signal(signal.SIGTERM, server.close)
gevent.signal(signal.SIGINT, server.close)
server.start()
gevent.wait()
def log(message, *args):
message = message % args
sys.stderr.write(message + '\n')
if __name__ == '__main__':
main()
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