By default, the Jetty Server uses port 7070.
If for any reason you need to change this, you can do so by editing the bladerunner.conf file, in the conf folder of your BladeRunner installation, which (like the conf folder itself), is created when you run the bladerunner command.
The file is in YAML format, and the unmodified version will contain the following line, commented out by a hash character:
To alter the port number, remove the
# at the beginning of the line, and modify the parameter to the port you want to use instead.