That's interesting Jeff. If WinXP can do this, I was unable to find out how or to make it work by experimentation. I wonder if Windows is trying to limit the number of sockets in use? If it worked, you could have a socket per device that received only data sent from the device. But that's a socket and (in my case) a thread per device. I implemented recvfrom and now it's done one thread with a quick IP address look-up and dispatch to the object that would have had its own thread.
Thanks for replying, Bill >-----Original Message----- >From: [email protected] >[mailto:[email protected]] On >Behalf Of Jeff Barber >Sent: Thursday, July 16, 2009 1:13 PM >To: Mailing list for lwIP users >Subject: Re: [lwip-users] OT: Binding UDP in WinXP > >That's not true for the BSD socket API. Connect(2) has always worked >with UDP sockets as well. See, for example >"http://www.manpages.info/freebsd/connect.2.html"; which includes this >text: > If [the socket descriptor] is of type SOCK_DGRAM, this call > specifies the peer with which the socket is to be associated; this > address is that to which datagrams are to be sent, and the only >address > from which datagrams are to be received. > >The openbsd, sunos, and linux manual pages all have similar text. >Using connect allows one to use recv(2) instead of recvfrom(2) (since >the address of the remote peer is already known). > >Jeff > >On Wed, Jul 15, 2009 at 6:32 PM, David Empson<[email protected]> wrote: >> You can't. :-) >> >> Looking at the BSD socket API in general, the point of bind() is to >specify >> a local "name" (family, address and port) for the socket. It doesn't >say >> anything about the remote IP address or port. >> >> With TCP, you must bind() the listening socket (since it requires a >well >> known port) but typically don't bind the connecting socket unless it >also >> needs to use a fixed port. >> >> With UDP, you typically bind() any socket which needs to receive data >on a >> well known port, but don't bother for one that is just sending data >(or one >> which will remain open for receive, and other devices find out which >port >> you are using due to receiving data from you or through other means). >> >> The address in the bind() call must be one of your own IP addresses, >> typically that of a specific network interface. You can use IP_ADDRANY >to >> leave your socket able to communicate via any network interface. >> >> An unbound socket will use IP_ADDRANY and a randomly assigned port >number. >> >> If you are receiving UDP data from two devices on the same socket >(i.e. both >> are sending data to the same port), you call recvfrom() and use the >address >> passed back via the "from" parameter to distinguish them. >> >> ----- Original Message ----- >> >> From: Bill Auerbach >> To: 'Mailing list for lwIP users' >> Sent: Thursday, July 16, 2009 6:53 AM >> Subject: [lwip-users] OT: Binding UDP in WinXP >> >> After half a day at this problem that I cant solve, I figure someone >here >> might say the answer is, You cant and Ill know I have a big >problem. J >> >> I can send UDP data from WinXP to lwIP using SentTo no problem. I can >> receive from lwIP if I use the port and IP_ADDRANY. I realized with 2 >of my >> devices connected I have a problem so I tried to bind the UDP socket >in >> WinXP to the IP address and port of the lwIP device (I know it from a >prior >> UDP here I am broadcast). WinXP refuses to bind (or connect) to a >> specific IP address. I know Im missing something and spent half the >day >> not finding it. How do you bind a WinXP SOCK_DGRAM socket to a remote >IP >> address and port? >> >> _______________________________________________ >> lwip-users mailing list >> [email protected] >> http://lists.nongnu.org/mailman/listinfo/lwip-users >> > > >_______________________________________________ >lwip-users mailing list >[email protected] >http://lists.nongnu.org/mailman/listinfo/lwip-users _______________________________________________ lwip-users mailing list [email protected] http://lists.nongnu.org/mailman/listinfo/lwip-users
