En Sat, 13 Dec 2008 18:19:29 -0200, Emanuele D'Arrigo <man...@gmail.com>
escribió:
I'm trying to replicate the positive results of the Client/Server
scripts from the thread "Bidirectional Networking", but this time
using a Process/SubProcess architecture.
The SubProcess, acting as a server, is working just fine. But the
Process executing the SubProcess, the client, somehow doesn't hear any
of the standard output from the SubProcess. What am I missing?
(Pipes don't work the same as sockets, although unix-like systems try hard
to hide the differences...)
- you have to close server.stdin when you don't have more data to send.
The server will see an end-of-file and knows it has to exit the loop. Same
thing on the client side.
- you have to wait until the server answers, else it will get a "broken
pipe" error or similar.
- end-of-file, in Python, is detected when a read/readline returns an
empty string
- you sent "Stop!" without a \n - readline() on the server side would wait
forever; it doesn't matter in the code below because server.stdin is
explicitely closed.
Below are the modified version of your programs:
#clientTest.py
import sys
import threading
from time import sleep
from subprocess import Popen, PIPE
## Server Thread
class ListenerThread(threading.Thread):
def __init__(self, inChannel):
threading.Thread.__init__(self)
self.inChannel = inChannel
def run(self):
while True:
data = self.inChannel.readline()
if not data: # data=='' means eof
break
data = data.strip()
print("serverTest.py says: " + data)
print("Starting Client!")
server = Popen("python serverTest.py", stdin=PIPE, stdout=PIPE)
listenerThread = ListenerThread(server.stdout)
listenerThread.start()
server.stdin.write("Something very meaningful!\n")
server.stdin.write("Stop!")
server.stdin.close() # notify server: no more data
listenerThread.join() # wait until server closes channel
print("Client Stopped!")
# serverTest.py
import sys
print("Starting Server!")
while True:
data = sys.stdin.readline()
if not data: # data=='' means eof
break
data = data.strip()
print("SERVER RECV: '" + data + "'")
if(data == "Stop!"):
break
print("Server Stopped!")
--
Gabriel Genellina
--
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