ROS Master is running. Can't run 'rosinit'

Why can I not initialize a ROS core with 'rosinit'? I receive the following error:

'>>rosinit

The ROS master is already running on port 11311. Try connecting to this master or creating a new ROS master that uses a

different port.'

Upon trying 'rosshutdown' and attempting 'rosinit' again I recieve the same error:

'>> rosshutdown

>> rosinit

The ROS master is already running on port 11311. Try connecting to this master or creating a new ROS master that uses a

different port.'

What are the next steps I should try to get this running correctly?

Answer 1

[Cam Salzberger]

Hey Michael,

It sounds like there is already a ROS Master running on your machine on the port 11311, but (probably) not having been created within your current MATLAB session. My assumption is that you have started a roscore/roslaunch script from another terminal, or have another MATLAB instance running that has run rosinit.

If you want to connect to it, provide the Master URI to rosinit. If you don't want that Master running, shut it down from the appropriate terminal or other MATLAB instance. If you can't find any other terminal or MATLAB instance running, close down MATLAB and check your process monitor (task manager) to see if there are any hanging processes running that shouldn't be.

If you are looking to have two instances of MATLAB running with two different ROS networks at the same time on the same machine, I recommend using the ros.Core API to start the Master, specifying different ports. Then you should be able to either connect to that Master with rosinit, specifying the URI to that specific Master, or use ros.Node to connect directly (and ros.Publisher, ros.Subscriber, etc. to set up your communications for that node).

-Cam

[Arun Ravindran]

I am using MATLAB R2020a (Trial version) and i also get the same error.

>> rosinit

The ROS master is already running on port 11311. Try connecting to this master or creating a new ROS

master that uses a different port.

All i did was to start MATLAB and run rosinit

....................

core= ros.Core

Error using ros.Core/launchPublicCore (line 166)

The ROS master is already running on port 11311. Try connecting to this master or creating a new ROS

master that uses a different port.

Error in ros.Core (line 86)

loopBackError = obj.launchPublicCore(port);

...................................

>> core = ros.Core(12000)

Error using ros.Core/launchPublicCore (line 166)

The ROS master is already running on port 12000. Try connecting to this master or creating a new ROS

master that uses a different port.

Error in ros.Core (line 86)

loopBackError = obj.launchPublicCore(port);

................................................

I am behind a company proxy.

[Cam Salzberger]

That definitely seems like an issue. i don't know for sure whether or not the company proxy may have something to do with the issue.

I would suggest contacting technical support at this point. They should be able to get more in-depth with your particular machine, and can walk through the internal code with you, and get more information out of the error.

-Cam

Answer 2

[Johannes Møgster]

for what it`s worth, rosinit would freeze on me too, ros.Core(11311) told me ROS was already running (it was not) and to try another port, tried ros.Core(11312) worked fine.

Seemed like something was running on 11311, so I opened cmd, netstat -a -n -o, found the PID of something that was running on 11311, opened task manager, details, found the PID and stopped whatever was running. rosinit worked again. Same error after reboot though.

Does anyone know how to avoid stuff blocking my precious 11311 port?

[Cam Salzberger]

If you can determine what program it was, you may be able to change its settings to use a different port. If not, or if it doesn't have settings, any computer-wide setting done to block programs from using 11311 would also block ROS.

There's nothing particular special about 11311 other than it being the default port. Feel free to use any port that works for you, so long as your other ROS machines target it.