Connect Android emulator to a remote system

I have 2 systems ubuntu A and B.

IP Address: 192.168.0.5 B IP Address: 192.168.0.3

System A runs an Android emulator. I have a TCP Client application that needs to communicate with system B.

Since Android applications can “see” localhost (like 10.0.2.2), the client application sends a message at 10.0.2.2 to the Pb port.

Now I assume that System A should see that any message that it receives on its localhost (for example, 127.0.0.1, which is 10.0.2.2 for the emulator) in the Pb port should be redirected to System B 192.168.0.3 on the port Pb. Therefore, I installed the following in System A:

echo "1" </ Transactions / Systems / Net / ipv4 / ip_forward

sudo iptables -t nat -A PREROUTING -p tcp -s 127.0.0.1 -d 127.0.0.1 -dport Pb -j DNAT -to-destination 192.168.0.3:Pb

System B starts the TCP server on IP 192.168.0.3 and the Pb port

Using these rules on systems A and B, I run the android emulator for system A, and then the TCP Client application on Andoid.

The Wireshark tool shows packets reaching 127.0.0.1, but my server in System B does not receive any packets at all :(

What's wrong?

--------------------              --------------------------

  System A                        System B
  192.168.0.5 wlan0               192.168.0.3 wlan0
  127.0.0.1   lo                  127.0.0.1 lo
                <---------------->

  Android EMULATOR                TCP Server
  TCP CLient App                  at 192.168.0.3, port Pb
  at 10.0.2.2
----------------------            ----------------------------

Please, help.