This is a note describing the steps needed to forward TCP and UDP traffic to the Android Emulator.

Sometimes when developing an application one need to connect and send data from the host machine to the app running in an Android Emulator. In order to do that there are some tricks needed for forwarding the traffic.

Forward TCP traffic to Android Emulator

Forwarding TCP traffic to android emulator is simple. Just use the adb tool like this to forward host port 2222 to port 3333 on the Android emulator:

$ adb forward tcp:2222 tcp:3333

Check with

$ adb forward --list
emulator-5554 tcp:2222 tcp:3333

Forward UDP traffic to Android Emulator

The forward command in adb tool can only forward TCP traffic. In order to forward UDP traffic one need to telnet into the emulator itself and run a command.

First you need the emulators auth token. The auth token can be found by doing

$ cat ~/.emulator_console_auth_token

When the emulator is running it opens a control port on port 5554, Connect to the port using telnet and use the command

auth <token>

to authenticate. Then use the redir command to forward host UDP port 2222 to emulator port 3333. This is the complete procedure:

$ telnet localhost 5554
Trying ::1...
Connected to localhost.
Escape character is '^]'.
Android Console: Authentication required
Android Console: type 'auth <auth_token>' to authenticate
Android Console: you can find your <auth_token> in
auth sU6**********XS8
Android Console: type 'help' for a list of commands
allows you to add, list and remove UDP and/or PORT redirection from the host to the device
as an example, 'redir  tcp:5000:6000' will route any packet sent to the host's TCP port 5000
to TCP port 6000 of the emulated device

available sub-commands:
    list             list current redirections
    add              add new redirection
    del              remove existing redirection

redir add udp:2222:3333
redir list
udp:2222  => 3333

So as seen in the redir list command host UDP port 2222 is now forwarded to port 3333 on the emulator.


Android Developer - emulator networking