I also have problems with multiple machines.

I tried the suggestions of this closed questions:

https://answers.ros.org/question/38694/running-ros-across-multiple-machines/

I just tried the suggested answer of SamsAutonomy from this questions and it also resulted in the same result as below (see below):

Master: cmd_vel topic published data can be seen

Slave: cmd_vel is rostopic list listed, but no data is coming in.

I can ping and netcat in both directions. ~/.bashrc is sourced.

Desktop computer: Master running roscore

IP: 192.168.178.34

Hostname: user-MS-7A32

Ubuntu 18.04 - ROS Melodic

/etc/hosts

127.0.0.1 localhost

127.0.1.1 user-MS-7A32

192.168.178.44 raspberrypi

::1 localhost ip6-localhost ip6-loopback

ff02::1 ip6-allnodes

ff02::2 ip6-allrouters

Ff00::0 ip6-mcastnet

fe00::0 ip6-mcastprefic

~/.bashrc

export ROS_HOSTNAME=user-MS-7A32

export ROS_MASTER_URI=http://user-MS-7A32:11311

export ROS_IP=192.168.178.34

Raspberry Slave Robot: Not running roscore

IP: 192.168.178.44

Hostname: raspberrypi

Debian Buster - ROS Melodic

/etc/hosts

127.0.0.1 localhost

127.0.1.1 raspberrypi

192.168.178.34 user-MS-7A32

::1 localhost ip6-localhost ip6-loopback

ff02::1 ip6-allnodes

ff02::2 ip6-allrouters

~/.bashrc

export ROS_HOSTNAME=raspberrypi

export ROS_MASTER_URI=http://user-MS-7A32:11311

export ROS_IP=192.168.178.44

Setup 1:

Master:

$ roscore

$ rostopic echo /cmd_vel

Slave:

$ rosrun teleop_twist_keyboard teleop_twist_keyboard.py

$ rostopic echo /cmd_vel

Result:

cmd_vel topic published data can be seen on both machines.

Setup 2:

Master:

$ roscore

$ rosrun teleop_twist_keyboard teleop_twist_keyboard.py

$ rostopic echo /cmd_vel

Slave:

$ rostopic echo /cmd_vel

Result:

Master: cmd_vel topic published data can be seen

Slave: cmd_vel is rostopic list listed, but no data is coming in.

I also tried the suggestion:

Changes on Master:

~/.bashrc

export ROS_MASTER_URI=http://192.168.178.34:11311

Can somebody tell me where my configuration mistake is?