Hi Dod.. No problem, and yes I also get hit by things like this, not only in software!...
Trouble is, the longer we keep fixing these sort of things, the more of them we get to do! Supose it keeps us out of trouble, or does it?.. Cheers. Dave B. > -----Original Message----- > From: Dod [mailto:[EMAIL PROTECTED] > Sent: Monday, March 10, 2008 10:29 AM > To: ICS support mailing > Subject: Re: [twsocket] Problem using same UDP port for both > listen and send > > 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 > DB> bit unproductive, as how would you inform any likely > clients (not on > DB> the same machine) what server port to connect to?... > > DB> Best I think to pick a specific port number to start with for the > DB> server to create and listen on, and then let the clients pick a > DB> unused port for 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 > DB> not generaly on the same physical machine for both a client and > DB> server, 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 > DB> client 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 > DB> connect 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 > DB> malicious 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. > DB> www.palmercook.co.uk > > > 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
