cant connect to udp port on external computer

mardek01

cant connect to udp port on external computer

in Contributed Library Questions • 8 months ago

Hi,

I am using the udp library. My processing sketch retrieves data from udp port 6666. And this works fine when I am on the same machine. I can connect and receive data from localhost and from '127.0.0.1'. This is a win XP machine. I have put the firewall off. Unfortunately I cant run my processing code on an other computer (PC or MAC) and receive the data from this machine. It says it cant bind to this port.

So my problem is that I can bind when on the same machine (XP) and cannot bind when i am on an other machine.

I think this has something to do with rights or so but I just dont know where to start. Does anayone know how to connect to an other IP on the same network with udp library.
http://ubaa.net/shared/processing/udp/

regards,
MArtijn

Replies(5)

buzlityr

Re: cant connect to udp port on external computer

5 months ago

Was anyone able to answer this question? I'm also trying to understand UDP programming using processing.org. I assumed that I needed to use the new udp() to create a datagram for the receive path (with my local IP) and another one for the transmit path (with the IP of the other computer). But when I try to run, I get an "open socket failed" error. Everything seems to work fine if I do not open a socket on the remote IP but use udp.send() with the remote IP/port by itself. Does udp.send open the remote port automatically? I was assuming (but may be wrong) that I need to open the port in order to write to it.

GoToLoop

Re: cant connect to udp port on external computer

5 months ago

It's just a little knowledge I've got about remote connections:

If your machine is the one which tries to initiate a connection to a remote one through a port, the router of that remote LAN has to be setup to redirect a connection through that port to that target machine from that LAN.

Or at least, instead of a formal port forwarding, a DMZ to that machine there!

Another method is that the target program running on that remote machine opens itself a port thru' UPnP.

As most smart clients do like µTorrent, Transmission, etc.

In short, the target remote machine has to do anything to get a port forwarding to itself, becoming a server,

before any other machines try to establish a connection to it.

Otherwise, it gets stuck on that remote LAN's router!

As it doesn't know which machine that port connection belongs to!

And lastly, http://miniupnp.free.fr/ is a very good program to run on target remote machine

to open ports through UPnP & NAT-PMP!

buzlityr

Re: cant connect to udp port on external computer

5 months ago

Thanks. I'll have to look into the DMZ further.

My original question was supposed to be simpler though, i.e., why I don't need to (and can't) do a new udp() with a remote IP. If I do, I get a can't connect error. I can only do a new udp() with a local IP.

GoToLoop

Re: cant connect to udp port on external computer

5 months ago

I can only do a new udp() with a local IP.

You can only take the initiative to establish a connection to a machine belonging to another LAN

from a port which is ALREADY opened!

Otherwise, your attempt connection doesn't get past that remote LAN's router!

Port-forwarding, DMZ, UPnP, etc. are techniques

which the remote machine can deploy to setup its LAN's router for it!

Once all's OK there, that machine can be considered a server, and yours its client!

buzlityr

Re: cant connect to udp port on external computer

4 months ago

I see. Thanks.

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