With the use of the GroLink Project GroIMP can be started as an API server, that can handle Http-requests.
Starting with GroIMP 2.1 the API application is included and can be started with the following command:
java -Xverify:none -jar core.jar --headless -a api
This starts a local web server, the default port is 58081, this can be changed either in the preferences panel in the GUI or by adding -Xport=58080 to the command above.
A more in-depth explanation of GroIMP arguments can be found here.
Now the API can be reached at http://localhost:58081/api. This will return an error message since no command was given.
While the API is running, it is possible to send the commands defined in the plugin directly or by using a client library. For now, there are libraries in python and R.