autoreconf -iv
./configure
make

make install

Usage: tcpkali [OPTIONS] <host:port> [<host:port>...]
Where OPTIONS are:
  -h, --help                  Print this help screen, then exit
  --version                   Print version number, then exit
  --verbose <level=1>         Verbosity level [0..3]

  --ws, --websocket           Use RFC6455 WebSocket transport
  -c, --connections <N=1>     Connections to keep open to the destinations
  -r, --connect-rate <R=100>  Limit number of new connections per second
  --connect-timeout <T=1s>    Limit time spent in a connection attempt
  --channel-lifetime <T>      Shut down each connection after T seconds
  --channel-bandwidth <Bw>    Limit single connection bandwidth
  -l, --listen-port <port>    Listen on the specified port
  -w, --workers <N=24>        Number of parallel threads to use
  -T, --duration <T=10s>      Load test for the specified amount of time

  -e, --unescape-message-args Unescape the following {-m|-f|--first-*} arguments
  --first-message <string>    Send this message first, once
  --first-message-file <name> Read the first message from a file
  -m, --message <string>      Message to repeatedly send to the remote
  -f, --message-file <name>   Read message to send from a file
  --message-rate <R>          Messages per second to send in a connection

  --statsd                    Enable StatsD output (default disabled)
  --statsd-host <host>        StatsD host to send data (default is localhost)
  --statsd-port <port>        StatsD port to use (default is 8125)
  --statsd-namespace <string> Metric namespace (default is "tcpkali")

  --latency-marker <string>   Measure latency using a per-message marker

And variable multipliers are:
  <R>:  k (1000, as in "5k" is 5000)
  <Bw>: kbps, Mbps (bits per second), kBps, MBps (bytes per second)
  <T>:  ms, s, m, h, d (milliseconds, seconds, minutes, hours, days)

tcpkali 127.0.0.1:80

tcpkali --message '$' localhost:echo
tcpkali -m '$' localhost:echo

tcpkali --connections 10000 yahoo.com:80 google.com:80
tcpkali -c 10000 yahoo.com:80 google.com:80

tcpkali --connections 100 --listen-port 12345 127.0.0.1:12345
tcpkali -c100 -l12345 127.0.0.1:12345

tcpkali --listen-port 12345 --message "cookies" 127.0.0.1:12345
tcpkali -l 12345 -m "cookies" 127.0.0.1:12345

tcpkali --listen-port 12345 --duration 3h
tcpkali -l12345 -T3h

tcpkali --websocket --first-message "hello" 127.0.0.1:80

tcpkali --websocket --message "{}" 127.0.0.1:80

tcpkali --websocket --message "{}" --message-rate=1 127.0.0.1:80

kern.maxfiles=10000+2*N         # BSD
kern.maxfilesperproc=100+N      # BSD
fs.file-max=10000+2*N           # Linux

# For load-generating clients.
net.ipv4.ip_local_port_range="10000  65535"  # Linux.
net.inet.ip.portrange.hifirst=10000          # BSD/Mac.
net.inet.ip.portrange.hilast=65535           # (Enough for N < 55535)
net.ipv4.tcp_tw_reuse=1

# If using netfilter on Linux:
net.netfilter.nf_conntrack_max=N
net.netfilter.nf_conntrack_max=N/4