When I started using Rev, I ported over some of my very basic networking scripts, and thought I had got enough of them working to know what I was doing. Turns out there was one piece I missed, and I can't figure out how to do it in Rev.
I did both server and client for TCP, and the "peer-to-peer style UDP", and I did the UDP server-side - but I never got around to doing the UDP client-side part of it (because for that I just used the program I already had set up and running on another machine that didn't have Rev on it).
What I've always done for "client-server" style UDP is used a pair of adjacent port numbers - one for client->server, the other for server->client. I think you can often get away with just one - but using the pair means you can do much of your testing on a single machine.
Server pseudo-code:
accept datagram connections on port "4567" with message "gotPacket"
on gotPacket pRemote, pData put pRemote into pRemote set the itemDel to ":" add 1 to item 2 of pRemote open datagram socket to pRemote write "reply with " & param(2) to socket pRemote close socket pRemote end gotPacket
Now the echo client version, using standard system calls, is simply
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) r = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.connect( (HOST,PORT) )
# get the source port allocated, and listen on adjacent one reply_host, reply_port = s.getsockname() reply_port += 1 r.bind( (reply_host, reply_port) )
while 1 :
str = raw_input('type it')
s.send(str)
data = r.recv(1024)
print "Back came ", data
s.close()
Most of this translates simply into Rev - except I can't find the equivalent of getsockname(), which tells me the local IP address and port number which will be filled in as source addr, source port in the UDP packet. The server uses this to determine where to send its reply; source addr is, of course, just the IP address of the client machine (which I can get from hostAddress() once I have connected the socket) - but I don't see a way to find which source port will be chosen. Without that, I don't know which port to bind to in order to receive the server responses.
Is there a way to find that ?
Or, alternatively, is there a different way to set up a client-server UDP pair ? i.e. have a pre-defined port number used on the server, which is also configured in every client, but allocate the client ports dynamically.
Thanks -- Alex.
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