Re: Unable to listen properly on UDP port 4500
Thanks and noted. Definitely not a masochist... I will adjust my ports accordingly. Cheers! Chris On 2020/12/8 16:29, Philip Guenther wrote: : bleys; grep 4500 /etc/services ipsec-nat-t 4500/tcp ipsec-msft # IPsec NAT-Traversal ipsec-nat-t 4500/udp ipsec-msft # IPsec NAT-Traversal : bleys; sysctl net.inet.esp.udpencap net.inet.esp.udpencap=1 : bleys You're trying to use the ipsec ESP encapsulation port, which is enabled by default. If you're a masochist and likes making your life more difficult, you can use that port for your own purposes by disabling that sysctl. If you're not a masochist, use a different port. Philip Guenther
Re: Unable to listen properly on UDP port 4500
: bleys; grep 4500 /etc/services ipsec-nat-t 4500/tcpipsec-msft # IPsec NAT-Traversal ipsec-nat-t 4500/udpipsec-msft # IPsec NAT-Traversal : bleys; sysctl net.inet.esp.udpencap net.inet.esp.udpencap=1 : bleys You're trying to use the ipsec ESP encapsulation port, which is enabled by default. If you're a masochist and likes making your life more difficult, you can use that port for your own purposes by disabling that sysctl. If you're not a masochist, use a different port. Philip Guenther On Tue, Dec 8, 2020 at 4:13 PM Chris Johnson wrote: > Hello All, > > I am unable to set up a localhost netcat listener on UDP port 4500 that > responds to a client on that same host. I encountered this issue > attempting to test whether UDP 4500 was open on our departmental firewall. > > Simple test case: Fresh build of OpenBSD 6.8. No local network, no > packet filter, no iked running. > > # netstat -na -f inet | grep 4500 > [empty] > # fstat | grep 4500 > [empty] > > $ nc -ul localhost 4501 & > [1] 72638 > $ nc -u localhost 4501 > Z > Z > ^C > $ pkill nc > > [1]+ Stopped nc -ul localhost 4501 > $ nc -ul localhost 4500 & > [2] 70181 > $ nc -u localhost 4500 > Z > ^C > $ pkill nc > [2]- Terminated nc -ul localhost 4500 > > The server running on port 4500 does not echo. Why not? Is there > something obvious that I'm missing? > > I've tried this on three different OpenBSD 6.8 systems (all amd64). Is > UDP 4500 reserved in some way? Other ports I've tried work fine. Linux > and MacOS systems work fine on this port. > > Cheers, > > Chris > >
Unable to listen properly on UDP port 4500
Hello All, I am unable to set up a localhost netcat listener on UDP port 4500 that responds to a client on that same host. I encountered this issue attempting to test whether UDP 4500 was open on our departmental firewall. Simple test case: Fresh build of OpenBSD 6.8. No local network, no packet filter, no iked running. # netstat -na -f inet | grep 4500 [empty] # fstat | grep 4500 [empty] $ nc -ul localhost 4501 & [1] 72638 $ nc -u localhost 4501 Z Z ^C $ pkill nc [1]+ Stopped nc -ul localhost 4501 $ nc -ul localhost 4500 & [2] 70181 $ nc -u localhost 4500 Z ^C $ pkill nc [2]- Terminated nc -ul localhost 4500 The server running on port 4500 does not echo. Why not? Is there something obvious that I'm missing? I've tried this on three different OpenBSD 6.8 systems (all amd64). Is UDP 4500 reserved in some way? Other ports I've tried work fine. Linux and MacOS systems work fine on this port. Cheers, Chris
