The port is dynamically allocated now. You can determine actual port in use from the server-output log file. I found the same issue with the sonic-pi-cli tool, and proposed a solution over a year ago which has now been adopted in the latest version 0.1.3
If it does not detect the information in the log file then it assumes an earlier version of Sonic Pi and reverts to the previous port 4557.
A similar technique could be applied to the sonic-pi-tool.py script. In the meantime sonic-pi-cli will perform the same job.