I have a macbook pro running Catalina 10.15.1. However this issue has been present since at least Mojave.

After a reboot it runs fine for a while (up to about an hour but I haven't measured) and then most web requests start to fail. This does not affect Chrome which is my main browser, but for example running:

curl https://github.com
curl: (35) LibreSSL SSL_connect: SSL_ERROR_SYSCALL in connection to github.com:443


curl http://example.com
curl: (56) Recv failure: Connection reset by peer`

A restart will fix both these issues temporarily.

I've tried using brew to update curl and libressl but they're both up to date.

curl 7.64.1 (x86_64-apple-darwin19.0) libcurl/7.64.1 (SecureTransport) 
LibreSSL/2.8.3 zlib/1.2.11 nghttp2/1.39.2

How do I fix these connection issues?

  • What is the version of curl you have now? – Udhy Dec 19 '19 at 14:53
  • @Udhy version string is "curl 7.64.1 (x86_64-apple-darwin19.0) libcurl/7.64.1 (SecureTransport) LibreSSL/2.8.3 zlib/1.2.11 nghttp2/1.39.2" – Ian Newson Dec 19 '19 at 15:24
  • Try "networksetup -setv6off Wi-Fi" without quote from the terminal and it should resolve your issue. – Udhy Dec 19 '19 at 15:49
  • @Udhy Thanks, that didn't work even with sudo. Does it require a restart? – Ian Newson Dec 19 '19 at 16:06
  • networksetup -setv6off Wi-Fi - > works for me from the terminal and you should reboot to check it. – Udhy Dec 19 '19 at 16:13

There are two options that you can try;

First, try to run this command


And second, run the following command from your terminal:

networksetup -setv6off Wi-Fi

Reboot the machine and check it.

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This can happen because of network or connection issues.

You have to find out where the issue is coming from.

  • First try connecting through a mobile or a 4G connection to see if the issue is in your machine or the local network.
  • If the issue is with the machine, try disabling firewalls, Anti-virus programs etc to find the root of problem.
  • It can happen because of an incorrect IP v6 configuration. Try disabling IPv6 locally.
  • Go to System Preferences > Network > TCP/IP > Change Configure IPv6 to Link-local only.
  • If you have access to the router, try disabling IPv6 network. If that solves the issue, then there's a misconfiguration on router.
  • After you found the cause, fix it and enable firewalls and anti-virus programs.
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