I don't use SC, but I'll check anyway if some years ago I installed it and then forgot about it.

It is a multicast address - I might be able to change it to the normal broadcast address, but I wouldn't count on it. So for now, it's better to assume that this can't be changed.

Hmmm... 57120 happens to be the default port of sclang (the SuperCollider language interpreter). Could it be that sclang(.exe) is running? Check the task manager to be sure.

Explanation: Generally, only one application can listen to a port at a time. Normally, applications will just refuse to bind to ports that are already taken. However, Pd sets the SO_REUSEADDR socket option, which allows to bind to an existing port.

This is needed for TCP sockets, because they typically "linger" for a while after you close them. If you close and immediately reopen a patch, [netreceive] would refuse to bind.

However, we probably should not set SO_REUSEADDR for UDP sockets because it doesn't do anything useful. On the contrary, it just causes confusion because [netreceive -u] does not post an error if the port is already taken.

Christof

On 10.01.2024 23:08, João Pais wrote:

Hi everyone,

I'm trying to receive some UDP data from a mobile device into Pd. The data arrives in the computer (windows or ubuntu), here is a description from wireshark:

Frame 173: 90 bytes on wire (720 bits), 90 bytes captured (720 bits) on interface \Device\NPF_{2ADD2685-ACB9-4C51-B708-F1F62FAE86C7}, id 0
Ethernet II, Src: XiaomiCommun_1d:0e:fd (4c:e0:db:1d:0e:fd), Dst: IPv4mcast_01 (01:00:5e:00:00:01)
Internet Protocol Version 4, Src: 192.168.178.34, Dst: 224.0.0.1
User Datagram Protocol, Src Port: 43641, Dst Port: 57120
Data (48 bytes)

But with [netreceive -u -b 57120] (or any other options to netreceive) no data comes into Pd. Does anyone have any suggestion on how to receive the data?

When is sent to 224.0.0.1, the data gets into the computer but not into Pd. But if other udp data is sent to the broadcast ip (192.168.178.255) from the same device, it does get also into Pd.

Frame 31: 66 bytes on wire (528 bits), 66 bytes captured (528 bits) on interface \Device\NPF_{2ADD2685-ACB9-4C51-B708-F1F62FAE86C7}, id 0
Ethernet II, Src: XiaomiCommun_1d:0e:fd (4c:e0:db:1d:0e:fd), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Internet Protocol Version 4, Src: 192.168.178.34, Dst: 192.168.178.255
User Datagram Protocol, Src Port: 42797, Dst Port: 57120
Data (24 bytes)

Best,

Joao

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