Provided by: iperf3_3.1.3-1_amd64 bug


       iperf3 - perform network throughput tests


       iperf3 -s [ options ]
       iperf3 -c server [ options ]


       iperf3  is  a tool for performing network throughput measurements.  It can test either TCP
       or UDP throughput.  To perform an iperf3 test the user must establish both a server and  a


       -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.

       -1, --one-off
              handle one client connection, then exit.


       -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.   Setting
              the  target  bandwidth  to 0 will disable bandwidth limits (particularly useful for
              UDP  tests).   On  platforms  supporting  the  SO_MAX_PACING_RATE   socket   option
              (currently  only  Linux),  fair-queueing  socket-level  pacing,  implemented in the
              kernel, will be used.  On other platforms,  iperf3  will  implement  its  own  rate

              disable  the use of fair-queueing based socket-level pacing with the -b option, and
              rely on iperf3's internal rate control.

       -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)

       --cport port
              bind data streams to a specific client port (for TCP and UDP only,  default  is  to
              use an ephemeral port)

       -P, --parallel n
              number of parallel client streams to run

       -R, --reverse
              run in reverse mode (server sends, client receives)

       -w, --window n[KM]
              window  size  /  socket  buffer size (this gets sent to the server and used on that
              side too)

       -M, --set-mss n
              set TCP/SCTP maximum segment size (MTU - 40 bytes)

       -N, --no-delay
              set TCP/SCTP 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)

       -X, --xbind name
              Bind SCTP associations to a specific subset of links using sctp_bindx(3).  The  --B
              flag  will  be  ignored  if this flag is specified.  Normally SCTP will include the
              protocol addresses of all active links  on  the  local  host  when  setting  up  an
              association.  Specifying  at  least one --X name will disable this behaviour.  This
              flag must be specified for each link to be included  in  the  association,  and  is
              supported  for  both iperf servers and clients (the latter are supported by passing
              the first --X argument to bind(2)).  Hostnames are accepted as  arguments  and  are
              resolved  using getaddrinfo(3).  If the --4 or --6 flags are specified, names which
              do not resolve to addresses within the specified protocol family will be ignored.

       --nstreams n
              Set number of SCTP streams.

       -Z, --zerocopy
              Use a "zero copy" method of sending data, such as sendfile(2), instead of the usual

       -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, --congestion algo
              Set  the  congestion control algorithm (Linux and FreeBSD only).  An older --linux-
              congestion synonym for this flag is accepted but is deprecated.

              Get the output from the server.  The output format is determined by the server  (in
              particular,  if  the server was invoked with the --json flag, the output will be in
              JSON format, otherwise it will be in human-readable format).  If the client is  run
              with  --json,  the  server  output  is  included  in a JSON object; otherwise it is
              appended at the bottom of the human-readable output.


       A list of the contributors to iperf3 can be found  within  the  documentation  located  at