udp port 67, multiple listener in windows 11

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sleepsleep

Joined: 05 Oct 2006
Posts: 13344
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sleepsleep 25 Apr 2025, 19:49

in windows cmd.exe

Code:

C:\Windows\System32>netstat -anb | findstr ":67"
 UDP    172.25.64.1:67         *:*

that ip is hyper-v default switch, and the process belong to ics, under service name SharedAccess

i downloaded tiny dhcp server, https://softcab.com/archive/dhcp-server.php and run it

Code:

C:\Windows\System32>netstat -anb | findstr ":67"
  UDP    172.25.64.1:67         *:*
  UDP    172.25.64.1:67         *:*
  UDP    192.168.43.220:67      *:*

now we can see both are listening 67 udp, so i tried to use golang and write a dhcp that listen udp port 67 but denied,

Code:

Found interface 'vEthernet (Default Switch)' with IP address: 172.25.64.1
Failed to listen on 172.25.64.1:67: listen udp4 172.25.64.1%vEthernet (Default Switch):67: bind: Only one usage of each socket address (protocol/network address/port) is normally permitted.

so how come it can listen, but my program can't?

25 Apr 2025, 19:49

macomics

Joined: 26 Jan 2021
Posts: 1149
Location: Russia

macomics 25 Apr 2025, 20:33

Most likely, one of the processes received a copy of the handle after creation with InheritHandles=True
Two ports in the same process are open on different system interfaces.

25 Apr 2025, 20:33

sleepsleep 26 Apr 2025, 22:39

i tested the following, listening in 0.0.0.0

i can receive discover from hyper-v client since it posted to broadcast, but to offer it from 0.0.0.0 is possible or impossible idk yet, do i need to bind hyper-v gateway in this case 172.25.64.1 to offer 172.25.64.100?

btw, am using

"github.com/insomniacslk/dhcp/dhcpv4"
"github.com/insomniacslk/dhcp/dhcpv4/server4"

26 Apr 2025, 22:39

sleepsleep 15 May 2025, 21:46

i found a new way to doing this without coding, by using a loop adapter, wireguard and new-netnat ps command

but too bad, it doesnt seem to bypass isp hotspot restrictions,

still finding ways to accomplish this objective

15 May 2025, 21:46

sleepsleep 16 May 2025, 05:20

wireguard, every proxy, seems to accomplish what i wanted, but not so stable, more testing required

16 May 2025, 05:20

sleepsleep 16 May 2025, 18:49

i figured out, maybe the seamless and easiest method would be getting an old phone and rooted it, Laughing

16 May 2025, 18:49

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