I recently updated my home network to a dual stack IPv4/IPv6.
I run a speedtest via iperf3 to iperf.stealth.net
Since switching to the dual stack, that test fails with the following error:
2026-04-18T02:01:59-04:00 INFO ../src/internal/speedtest/iperf.go:96 > Starting iperf3 test enable_download=true enable_jitter=false enable_upload=true server_host=iperf.stealth.net:5201
2026-04-18T02:01:59-04:00 ERROR ../src/internal/scheduler/scheduler.go:194 > Error running scheduled test error="iperf3 test failed: download test failed: iperf3 failed: stdout={\"event\":\"error\",\"data\":\"unable to connect to server - server may have stopped running or use a different port, firewall issue, etc.: Connection refused\"}\n{\"event\":\"end\",\"data\":{}} stderr=warning: Report format (-f) flag ignored with JSON output (-J) - exit status 1" schedule_id=7
When I run the test manually on the machine, it connects to an IPv6 address and runs successfully.
I recently updated my home network to a dual stack IPv4/IPv6.
I run a speedtest via iperf3 to iperf.stealth.net
Since switching to the dual stack, that test fails with the following error:
When I run the test manually on the machine, it connects to an IPv6 address and runs successfully.