I maybe didnt express myself correctly. I use Maxmsp as an OSC client. On the other side there is an OSC server that replies to the max max msp client on the udp port number that was used to send the OSC request. That is my question : is it possible to define the port number that is used to send the request ? And not the one of the target of the message.
I understand your question and no, there is no way to tell [udpsend] the outgoing port to use (at least, there is no way that I was aware of). In most cases, mono-directional networking tools will bind to `port 0' for outgoing connections (which means that the OS assigns a freely available random outgoing port), and I think [udpsend] does just the same. However, even if you could find out the outgoing port (which you can do with, for example, Wireshark) you couldn't really use that information, as it usually changes with each message...
the second parameter defines the port on which the remote machine listens to incoming messages. The question of the OP is whether there was an option to set the port used by the sender machine to send those same messages. My answer was that, AFAIK, there is no way to set this port from Max.
When you send an UDP message, it contains both the source and destination ports within the packet header, this is why I wrote that one could gather this information, if needed, with a network protocol analyser (eg. Wireshark), but since mono-directional solutions usually don't expect any response from the remote host, the source port number is usually set to 0 in these cases.
It might sound confusing at first, but one must distinguish between the outgoing port used by the sender host to send the messages out and the incoming port on which the receiver host is listening. In most cases, the outgoing port is simply irrelevant, but in very special cases (like the one described by the OP) you simply can't live without knowing the so-called source port. I've worked a few years ago with an ethernet-controlled microcontroller which also used the source port of the sender machine to send back the messages, and it took us a while to solve the scenario (in fact, this was the initial project which led me to launch my library).
You're welcome. Actually, I wonder how you would solve this scenario, so if you come up with a solution, I'd be interested in reading about it.
BTW, in my case, I finally managed to re-write the microcontroller itself to send the responses on a specified port instead of using the source port of my machine. However, if you don't have access to the source code of your OSC server, then this solution wouldn't work.
However, if your OSC server accepts TCP-based bi-directional connections as well, then you may experiment with the following solution, based on tools from The sadam Library:
The server settings related to the servers answer port would have to be accessible in the next update of the product, called meyersound galileo. The tcp is the actual spare solution and i'm just going to test it this afternoon.
@GB the patch that I made uses, in fact, OSC. Here's why: the purpose of the first pair of [udpsend]-[sadam.udpReceiver] is to catch the OSC stream created by [udpsend]. The reason is that my objects don't use OSC per se, but of course, they can catch any binary stream, including an OSC-formatted one. Then, this stream gets forwarded to the remote server by [sadam.tcpClient], which is a bi-directional TCP object, and as such, it would catch the stream sent back by the remote server. Now, the purpose of the last pair of objects ([sadam.udpSender]-[udpreceiver]) is to decode the OSC stream itself.
I know it's a bit tricky and it's a bit like a `dirty workaround', but at the end of the day, you get an OSC-formatted bi-directional TCP patch. So, the only real question remains, whether your server accepts TCP as well, or not?
the Server is able of getting both UDP and TCP OSC commands on one of his ports. The only difference is that it needs a four byte big endian length-in-bytes field before the osc packet like it is described in CNMAT's OSC 1.0 Standard. Keeping up trying.
Thanks all for this post - very informative. @GREGORBAUMANN - could you shed a little more light on how to format for TCP - I have it working fine with UDP - but i need TCP for this application. I know the packet size has to go first - but I am confused on how to do that.
For example - I have the OSC command - /TransportState 2