If you’re working on Windows and have HTC Sync installed, you may run into this error message. I hardly develop under Windows anymore, but since the Android plugin was a little buggy on OSX, I had to. This message drove me nuts and I did a little research: with netstat -o I could see which process ID was occupying the port and with Process Explorer I could see that HTC Sync itself was the culprit. I killed it but this didn’t help until I hindered it completely from auto-starting and restarted my machine afterwards.