Connecting to ROS on different machine (a robot)

ROS allows multiple computers to communicate and share topics and services via a local network. This feature is useful for remote testing and simulations, where different ROS nodes can run on multiple machines as if they were on a single computer.

To connect two example machines

1. Server (robot) with IP 192.168.68.101 and hostname uav
2. Client (notebook) with IP 192.168.68.5 and hostname notebook

you need to setup both the machines followingly.

Server computer (the robot)

Add following lines to ~/.bashrc:

export ROS_MASTER_URI=http://localhost:11311

Add following lines to the /etc/hosts:

192.168.68.5 notebook

Important (skipping these steps may kill ROS on the robot once it disconnects from Wifi):

• Do NOT export ROS_IP to ~/.bashrc.
• Remove the server's (the robot's) own hostname in /etc/hosts except of 127.0.1.1. More than one instance of 192.168.68.101 in /etc/hosts is not allowed. The top of the /etc/hosts file of the robot should look like:

127.0.0.1 localhost
127.0.1.1 uav

192.168.68.101 uav
192.168.68.5   notebook

Client computer (the notebook)

Add following lines to ~/.bashrc:

export ROS_MASTER_URI=http://192.168.68.101:11311

Add following lines to /etc/hosts:

192.168.68.101 uav

Troubleshooting

• Both IPs must be in the same subnet.
• Once you set up accordingly, you should be able to mutually ping the machines using only their hostnames (i.e., ping uav from notebook and vice versa).
• The hostnames must be exact. If the server has hostname uav, the client must specify uav and nothing else (e.g., uav1). In case it mismatches, ping will work between the machines but ROS topic transfer will NOT work.
• There can be multiple clients/servers in /etc/hosts, but the IPs must be unique.
• To be able to run ROS on the client again, set ROS_MASTER_URI back to export ROS_MASTER_URI=http://localhost:11311.
• For more information, follow to wiki.ros.org/ROS/Tutorials/MultipleMachines.