NOTE: This is a Maya issue that can happen with any renderer, including mental ray.

Like many other Maya users, I started getting this error when I tried to batch render:

// Error: line 1: Socket error creating command port SOLIDANGLE-PC:7835 (10048).

I checked the port 7835 with netstat, and that gave me a PID (process ID) of 109736

C:\Program Files\Autodesk\Maya2014\bin>netstat -ano | find "7835"
  TCP    XXX.XXX.XXX.XXX:7835   0.0.0.0:0              LISTENING       109736

But unfortunately, there didn’t seem to be any process with that PID, so I couldn’t kill it to free up the port. tasklist | find “109736” came up empty; there was no such PID in the Task Manager or Process Explorer; and TCP View said that PID was non-existent.

I was resigned to having to reboot my machine until I saw this. Then I used Process Explorer to find the process that was referencing the “non-existent” PID, and when I killed that process, I could batch render again from Maya.