filename="..."

while IFS="" read -r line; do
 echo "$line" | nc  
done    "$PIPE" 
    sleep 0.5            
done

socat tcp-listen:8080,fork EXEC:"ssh server.vpn.network.org nc localhost 8081"

ssh -f -N -D 54321 localhost

socat -v TCP:localhost:54321 EXEC:"ssh server.vpn.network.org nc -lkv localhost 54321"

$ sudo dbus-daemon --session

sudo lsof -c dbus-daemon -aU -a +E

$ echo  | nc -U /tmp/socket -v
$ echo  | socat - /tmp/socket
2024/12/12 22:55:47 socat E read(5, 0x61fb9e544000, 8192): Connection reset by peer

$ echo  | nc localhost 39231
nc: connect to localhost (::1) port 39231 (tcp) failed: Connection refused
Connection to localhost (127.0.0.1) 39231 port [tcp/*] succeeded!

-shellsession
user@host ~$ nc -luv 57303
Listening on [0.0.0.0] (family 0, port 57303)
NAV 2024/12/05 12:09:56.326365 DPS112 $GPZDA,121003.35,05,12,2024,,*63NAV 2024/12/05 12:09:56.422294 DPS112 $GPGGA,121003.00,3251.764736,N,07957.683827,W,2,12,0.8,21.38,M,-32.34,M,11.0,1007*72NAV 2024/12/05 12:09:56.470322 DPS112 $GPGLL,3251.764736,N,07957.683827,W,121003.00,A,D*71NAV 2024/12/05 12:09:56.518252 DPS112 $GPVTG,292.37,T,,M,0.0,N,0.0,K,A*30NAV 2024/12/05 12:09:57.302279 DPS112 $GPZDA,121004.33,05,12,2024,,*62NAV 2024/12/05 12:09:57.398194 DPS112 $GPGGA,121004.00,3251.764735,N,07957.683825,W,2,12,0.8,21.38,M,-32.34,M,12.0,1007*77NAV 2024/12/05 12:09:57.446220 DPS112 $GPGLL,3251.764735,N,07957.683825,W,121004.00,A,D*77NAV 2024/12/05 12:09:57.478284 DPS112 $GPVTG,63.00,T,,M,0.0,N,0.0,K,A*08NAV 2024/12/05 12:09:58.310157 DPS112 $GPZDA,121005.33,05,12,2024,,*63NAV 2024/12/05 12:09:58.390253 DPS112 $GPGGA,121005.00,3251.764738,N,07957.683824,W,2,12,0.8,21.37,M,-32.34,M,13.0,1007*74^C

-shellsession
user@host:~/tmp$ nc -lv 127.0.0.1:/dev/ttyUSB0
nc: getaddrinfo: Servname not supported for ai_socktype
user@host:~/tmp$ nc -lv 127.0.0.1:ttyUSB0
nc: getaddrinfo: Servname not supported for ai_socktype

apt install netcat-traditional

ip netns add ns1
ip netns add ns2

ip link add my_veth1 type veth peer name my_veth2

ip link set my_veth1 up netns ns1
ip link set my_veth2 up netns ns2

ip -n ns1 address add 1.2.3.4 dev my_veth1
ip -n ns1 route add 2.3.4.0/24 dev my_veth1

ip netns exec ns2 nc -u -l -p 8080

ip netns exec ns1 nc -u 2.3.4.5 8080  ns2 my_veth2 gives the same output

So I tried creating the ARP table entry manually...

And now apparently the UDP packet is being sent

> ns2 my_veth2 gives the same output

However, the first terminal that has the UDP netcat server running still doesn't output anything. Why?

---

**EDIT 3:** After doing all of the above, I tried assigning an IP address to my_veth2:

And now, when I send the UDP packet, I get this error in the terminal that is running netcat in listen mode:

# Terminal 1

apt install -y netcat-traditional tcpdump

ip netns add ns1
ip netns add ns2

ip link add my_veth1 type veth peer name my_veth2

ip link set my_veth1 up netns ns1
ip link set my_veth2 up netns ns2

ip -n ns1 address add 1.2.3.4 dev my_veth1
ip -n ns1 route add 2.3.4.0/24 dev my_veth1
ip -n ns2 address add 2.3.4.5 dev my_veth2
ip -n ns2 route add 1.2.3.0/24 dev my_veth2

ip netns exec ns2 nc -l -p 8080

# Terminal 2
ip netns exec ns1 tcpdump -i my_veth1

# Terminal 3
ip netns exec ns2 tcpdump -i my_veth2

# Terminal 4
ip netns exec ns1 nc 2.3.4.5 8080 <<< 'Hello world from network namespace ns1'

curl -d '{"Name":"Lorem", "age":"34"}' -H "Content-Type: application/json" -X POST http://:8080/ 

#!/bin/bash

while true; do
   echo -e "HTTP/1.1 200 OK\n\n
Title
$(date)" \
  | nc -l -k -p 8080 -q 1;
  nc -l -k -p 8080 -q 1 | cat - | grep -o '{...\+}';
done

This is nc from the netcat-openbsd package. An alternative nc is available
in the netcat-traditional package.
usage: nc [-46bCDdhjklnrStUuvZz] [-I length] [-i interval] [-O length]
          [-P proxy_username] [-p source_port] [-q seconds] [-s source]
          [-T toskeyword] [-V rtable] [-w timeout] [-X proxy_protocol]
          [-x proxy_address[:port]] [destination] [port]

nc -v -u -l -k 1234

nc -v -u 127.0.0.1 1234

mkfifo commands
mkfifo nc_responses

nc -k -l 47201 >commands nc_responses
done 

$ nc localhost 47201 <<< 'command 1'
$ nc localhost 47201 <<< 'command 2'
Ran command 1
$ nc localhost 47201 <<< 'command 3'
Ran command 2
$ nc localhost 47201 <<< 'command 4'
Ran command 3