Cannot get listener and talker working on two machines

edit

So I have two machines #1 and #2. I selected #1 as the master by

$ ssh #1
$ roscore

Now I opened a new terminal on #1 and then

$ export ROS_MASTER_URI=http://#1:11311
$ rosrun test1 listener

(Now the terminal is halting, waiting for messages to be posted on the topic)

Now I go on machine #2 and

$ ssh #2
$ export ROS_MASTER_URI=http://#1:11311
$ rosrun test2 talker

(The "Helloworld x" pops up continuously with incrementing x)

When I look at #1, the listener is still halting, I should expect "heard x" with incrementing x. If I try the two nodes on each machine, they work perfectly fine. It is just when I now use two machines.

Btw, they are in the same wireless network and I already check the network setup as in the ROS tutorial.

Could anyone solve my problem? Thanks.