iperf3 -c server [ options ]
-p ", " --port " n" set server port to listen on/connect to to n (default 5201)
-f ", " --format " " [kmKM] format to report: Kbits, Mbits, KBytes, MBytes
-i ", " --interval " n" pause n seconds between periodic bandwidth reports; default is 1, use 0 to disable
-F ", " --file " name" client-side: read from the file and write to the network, instead of using random data; server-side: read from the network and write to the file, instead of throwing the data away
-A ", " --affinity " n/n,m" Set the CPU affinity, if possible (Linux and FreeBSD only). On both the client and server you can set the local affinity by using the n form of this argument (where n is a CPU number). In addition, on the client side you can override the server's affinity for just that one test, using the n,m form of argument. Note that when using this feature, a process will only be bound to a single CPU (as opposed to a set containing potentialy multiple CPUs).
-B ", " --bind " host" bind to a specific interface
-V ", " --verbose " " give more detailed output
-J ", " --json " " output in JSON format
--logfile " file" send output to a log file.
-d ", " --debug " " emit debugging output. Primarily (perhaps exclusively) of use to developers.
-v ", " --version " " show version information and quit
-h ", " --help " " show a help synopsis
-s ", " --server " " run in server mode
-D ", " --daemon " " run the server in background as a daemon
-I ", " --pidfile " file" write a file with the process ID, most useful when running as a daemon.
-c ", " --client " host" run in client mode, connecting to the specified server
--sctp use SCTP rather than TCP (FreeBSD and Linux)
-u ", " --udp use UDP rather than TCP
-b ", " --bandwidth " n[KM]" set target bandwidth to n bits/sec (default 1 Mbit/sec for UDP, unlimited for TCP). If there are multiple streams (-P flag), the bandwidth limit is applied separately to each stream. You can also add a '/' and a number to the bandwidth specifier. This is called "burst mode". It will send the given number of packets without pausing, even if that temporarily exceeds the specified bandwidth limit.
-t ", " --time " n" time in seconds to transmit for (default 10 secs)
-n ", " --bytes " n[KM]" number of bytes to transmit (instead of -t)
-k ", " --blockcount " n[KM]" number of blocks (packets) to transmit (instead of -t or -n)
-l ", " --length " n[KM]" length of buffer to read or write (default 128 KB for TCP, 8KB for UDP)
-P ", " --parallel " n" number of parallel client streams to run
-R ", " --reverse run in reverse mode (server sends, client receives)
-w ", " --window " n[KM]" TCP window size / socket buffer size (this gets sent to the server and used on that side too)
-M ", " --set-mss " n" set TCP maximum segment size (MTU - 40 bytes)
-N ", " --no-delay " " set TCP no delay, disabling Nagle's Algorithm
-4 ", " --version4 " " only use IPv4
-6 ", " --version6 " " only use IPv6
-S ", " --tos " n" set the IP 'type of service'
-L ", " --flowlabel " n" set the IPv6 flow label (currently only supported on Linux)
-Z ", " --zerocopy " " Use a "zero copy" method of sending data, such as sendfile(2), instead of the usual write(2).
-O ", " --omit " n" Omit the first n seconds of the test, to skip past the TCP slow-start period.
-T ", " --title " str" Prefix every output line with this string.
-C ", " --linux-congestion " algo" Set the congestion control algorithm (linux only).