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Electronic Theatre Controls Inc

Troubleshooting Net3 Discovery on macOS


Eos, Cobalt, Concert, or other program on a Mac can't discover or connect to Net3/ACN devices including other consoles despite the network being in general working order.

Explanation of Issue

Net3/ACN products (including Consoles and Concert) all use a background service called "SLP" (Service Location Protocol) to discover other Net3/ACN devices on the network. A variety of problems can cause SLP to be unable to discover devices.

Checking status of or restarting SLP

Most of the time this is because the SLP daemon (SLPD) isn't running or isn't running properly. To check if SLPD is running on a Mac:

  1. Launch Eos, Cobalt, Concert, or other program you're attempting to use
  2. Open Activity Monitor and see if SLPD is listed.
  3. If not, refer to the additional steps below for starting SLPD. If it is listed, try stopping and re-starting SLPD (covered below) while the program is running and check for changes in behavior.

To shop and (re)start SLPD:

  1. Open a Terminal window
  2. Stop SLPD by typing "/usr/local/bin/stopslpd" without quotes in the terminal and press Enter.
  3. Check Activity Monitor and make sure no instances of SLPD are running
  4. Start SLPD by typing "/usr/local/bin/slpd" without quotes in the terminal and press Enter
  5. Check Activity Monitor and confirm SLPD is running

If you've tried stopping and restarting SLPD and the program is still not seeing network devices, try closing and re-launching the application and check for changes in behavior.

Other software blocking SLP

It is possible that other programs or services on your Mac could be using TCP port 427 (and blocking others from using it), which is necessary for SLP to function. In that case the offending program/service must be identified and closed/terminated. This can also occur on PCs, and on that platform network printer services (by Brother, Epson, HP, and other printer manufacturers) are the most common applications that also use TCP port 427.


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