Hello Dave, Thanx for this long answer, I am already aware of all the way it "should" be done, but I have to work on a very old client/server project for which the sources has been lost, so I need to keep the same way it actually works and do the patch thru a proxy that will emulate the original server way of managing it's UDP protocol.
Neverless, I found a workaround. Regards. DB> Unless you are using an existing known protocol, in which case you'd DB> idealy use one of the recognised existing port numbers.... Port 80, DB> 8008, 8080 for an HTTP server for example. DB> Letting the system pick a random port to listen on as a server is a bit DB> unproductive, as how would you inform any likely clients (not on the DB> same machine) what server port to connect to?... DB> Best I think to pick a specific port number to start with for the server DB> to create and listen on, and then let the clients pick a unused port for DB> them to talk with, to "connect" to your server that is listnening on a DB> known port. (UDP is a "connectionless" protocol of course) DB> It is posible to use the same port number to talk and listen on, but not DB> generaly on the same physical machine for both a client and server, DB> something has to be different between them, either the IP address, or DB> port number (or both) Or, the system hasn't a clue as to who what DB> where etc... DB> I guess you could define another localhost address, 127.0.0.2 for DB> example perhaps? AFIK there is no reason why a single machine can't DB> have multiple "local loopback" addresses. Unless someone else knows DB> different. Then you could use the same "Port" number for both client DB> and server, with care... DB> Check out... DB> http://www.iana.org/assignments/port-numbers DB> For typical known port numbers, some may be of use, many are worth DB> avoiding! (to keep script kiddies away, and to avoid strange connect DB> requests)... DB> Note, that ports in the range of... DB> 49152 through 65535 are avaialable for "Private or Dynamic" port DB> assignments. You can use any of them for anything, and being way up DB> there in "High Port Land" should be well out of the way of any malicious DB> port scanners looking for something to play with.... DB> Hope something helps.. DB> Cheers. DB> Dave B. >> -----Original Message----- >> From: Dod [mailto:[EMAIL PROTECTED] >> Sent: Thursday, March 06, 2008 2:48 PM >> To: ICS support mailing >> Subject: [twsocket] Problem using same UDP port for both >> listen and send >> >> Hello, >> >> I am working on something like : >> >> - Create Server UDP socket port 0 - Winsock select the >> listening port itself >> >> - I retrieve port number using GetSockName/.sin_port >> >> - The Socket server is now listening >> >> - I create a Socket client to connect to other machine >> but I set LocalPort with same socket number as the one >> retrieved by server socket >> >> - I .Connect the client to other machine and .Send the data >> >> All works fine on XP but the final program must run on NT4 >> and if I do this I get WSAEADDRINUSE ( 10048 ) Address already in use. >> >> If i set LocalPort to 0 before .Connect then all is fine of course. >> >> Any idea why NT4 cannot not set localport for UDP sending >> with same number as port used by a server socket ? May be an >> old NT4 Winsock limitation ? >> >> I know NT4 is old but I have to work on a very old server >> that can't be upgraded. May be some of you remember such limitation ? >> >> Regards. >> >> >> DB> This mail has been scanned by Palmer Cook Computer Services Limited. www.palmercook.co.uk -- To unsubscribe or change your settings for TWSocket mailing list please goto http://lists.elists.org/cgi-bin/mailman/listinfo/twsocket Visit our website at http://www.overbyte.be
