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I'm getting this error when connecting to a web server on port 6666 (http://myserver:6666/):

Error 312 (net::ERR_UNSAFE_PORT): Unknown error.

Is there an easy way to resolve this without rebuilding Chrome from source?

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up vote 44 down vote accepted

Right Click on Chrome shortcut >> Properties >>

Then Append --explicitly-allowed-ports=xxx to shortcut target


C:\Documents and Settings\User\Local Settings\Application Data\Google\Chrome\Application\chrome.exe --explicitly-allowed-ports=6666

Resource from here

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I missed this answer, thanks. I opened a separate question to understand which ports are safe/blocked by default:… – ripper234 Sep 13 '10 at 12:36
This answer is excellent... for Windows. It won't solve the problem for (for example) Mac. – Chris R May 3 '12 at 17:23
@ChrisR: Why? Does the --explicitly-allowed-ports switch not exist for Mac? – Dennis May 3 '12 at 17:35
Adding command line flags on the mac is a pain in the ass; if you add them to the app bundle they often get nuked in upgrades. – Chris R May 3 '12 at 17:39
@ChrisR: You should consider adding this to your question. – Dennis May 3 '12 at 17:44

You may be able to turn this off in Google Chrome, but you do so at your own risk. There is actually a good security reason why Chrome blocks these ports: Basically you open your browser up to being an open proxy for attackers to use to attack other services on your network.

For more information: Why does Chrome consider some ports unsafe?

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@JanHudec You are correct. – Case Jul 29 '14 at 20:36
+1 for the analysis in your blog post :) – cxw Aug 21 '15 at 16:52

As subanki said, you've got to add the -explicitly-allowed-ports option to your Chrome startup command.

In Ubuntu you can do this (as root) by editing the "google-chrome" script under your Chrome installation folder

You can get the directory by typing:

ls -la /usr/bin | grep chrome

Then, edit the "google-chrome" file adding the mentioned switch to the EXEC line:

exec -a "$0" "$HERE/chrome" "-explicitly-allowed-ports=6000" "$@"

Just change "6000" with the comma separated values you might need (example: -explicitly-allowed-ports=5000,6000,7000)

NOTE: for UNIX, the switch does NOT start with "--", it does with a single "-"

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For Mac:

/Applications/Google\\ Chrome --explicitly-allowed-ports=5000,6000,7000

for ports 5000, 6000, and 7000.

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Mac options with Automator (much better than manual launch)

On the Mac you can either start chrome with the terminal with " open /Applications/Google\ --args --explicitly-allowed-ports=PORTNUMBER" or create you own app with Automator


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Welcome to Super User! Please quote the essential parts of the answer from the reference link(s), as the answer can become invalid if the linked page(s) change. – DavidPostill Apr 14 at 13:44

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