iperf3 for Macpro

$ brew install iperf3
$ iperf3 -c 192.168.1.10

What it’s for

Speed Test measures your connection to the internet. iperf3 measures the link between two machines you control: this Mac and a NAS, a server, or another computer. It’s the standard way to find out what your Wi-Fi, cables and switches really carry.

Use it when

• Copying files to a NAS is slower than it should be.
• You want to compare Wi-Fi with a cable, or one access point with another.
• You’re testing a link to a server you run.

Reading the result

The other machine has to run an iperf3 server: iperf3 -s. Netutilus is the client, so it can’t be the server itself.

Click Add Server, enter its address, then Run. A run sends upload, then download, 10 seconds each by default.

• The large figure is what the receiver counted, the honest number. The sender’s figure is beneath it.
• Retransmits count data TCP had to send again. A few are normal; many mean a lossy link.
• The Per second table shows how steady the speed was. A dip every few seconds on Wi-Fi often means interference.
• Each result names the path it took: Wi-Fi, wired or VPN, with both addresses.

What you might see

• Nothing is listening. The server isn’t running, or a firewall blocks port 5201.
• Couldn’t connect, to a machine at home. Netutilus may need Local Network access. A button opens the setting.
• Upload and download very different. Common on Wi-Fi, where one side has the weaker antenna.

Options worth knowing

• Test Connection checks the server is reachable and free, without running a test.
• Advanced: parallel streams, duration, a bitrate limit, window size and IPv4 or IPv6, as in iperf3’s own options.
• Protocol: UDP sends at a target bitrate and reports jitter and lost datagrams, useful for calls and streaming.
• History keeps every run for each server.

Related

• Measure the speed between two of my machines.
• Wi-Fi Analyzer.