On 02.06.2021 16:55, Martin Peach wrote:
On Wed, Jun 2, 2021 at 9:58 AM Roman Haefeli reduzent@gmail.com wrote:
(replying to list as - I believe - you intended to)
On Wed, 2021-06-02 at 09:34 -0400, Martin Peach wrote:
On Wed, Jun 2, 2021 at 3:31 AM Roman Haefeli reduzent@gmail.com wrote:
On Tue, 2021-06-01 at 19:19 -0400, Martin Peach wrote:
A [udpsend] normally has a different port number to the one it sends to, but a [udpreceive] in the same Pd process can still receive on that port.
My understanding is that a client won't accept messages with a different source port than it has sent to. Also, such packets wouldn't be able to traverse NAT firewalls.
A udp packet almost always has a different source port from its destination. It's not the same as TCP as there is no real "connection" established or maintained, it's just fire and forget. I modified the udp objects in response to a request to do just that: send back to the same port.
You're absolutely right. I think my wording was not clear. Sorry for that.
When a client with bind port 52333 sends a packet to the server listening on port 5000, it won't accept response packets from the server with (matching) destination port 52333 and (different) source port 5001. [udpsend] on the server side cannot use bind_port=5000, because it is already used by [udpreceive]. And from what I see in the documentation, [udpsend] doesn't support setting a bind port, it seems to pick a random one (which is the normal thing to do when acting as a client, but not sufficient for a server response to a client request).
You're correct. I thought I had fixed that a few years back but I guess I hadn't. You could still have the server reply to the source port plus one, or something like that,
This doesn't solve anything regarding firewall + NAT.
Usually I have the client include its replyto port in a message.
But why? UDP sockets are already bidirectional. If you need to receive replies from the other end, just use the appropriate object, i.e. [iemnet/udpclient] or [netsend -u -b].
EDIT: I just saw your mail about [mrpeach/udpsndrcv] which probably achieves the same thing.
<rant> There is some persistent misunderstanding that UDP sockets can only be used in one direction. I think one reason is that many creative coding environments only provide very basic and limited networking objects, so users without a background in network programming think that's the way it should be done. In the "real world", a UDP server would simply send the reply to the source IP address + port obtained with recvfrom() while a TCP server would send its message to the client socket it received the message from. It's ironic that Pd doesn't provide an easy way for such a common task... </rant>
I just remembered that I already opened an issue: https://github.com/pure-data/pure-data/issues/949. Maybe it's time to also make a PR :-)
Martin
So, I believe my goal can (so far) only be achieved with [netsend -u]/[netreice -u] as Miller suggested. Mission accomplished.
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