this tools is to measure network performance. Iperf was originally developed by NLANR/DAST as a modern alternative for measuring TCP and UDP bandwidth performance

Server:
iperf -s -p 9999

Client:
iperf -c 192.168.122.150 -p 9999

Iperf features:
TCP
Measure bandwidth
Report MSS/MTU size and observed read sizes.
Support for TCP window size via socket buffers.
Multi-threaded if pthreads or Win32 threads are available. Client and server can have multiple simultaneous connections.
UDP
Client can create UDP streams of specified bandwidth.
Measure packet loss
Measure delay jitter
Multicast capable
Multi-threaded if pthreads are available. Client and server can have multiple simultaneous connections. (This doesn’t work in Windows.)

Where appropriate, options can be specified with K (kilo-) and M (mega-) suffices. So 128K instead of 131072 bytes.
Can run for specified time, rather than a set amount of data to transfer.
Picks the best units for the size of data being reported.
Server handles multiple connections, rather than quitting after a single test.
Print periodic, intermediate bandwidth, jitter, and loss reports at specified intervals.
Run the server as a daemon.
Run the server as a Windows NT Service
Use representative streams to test out how link layer compression affects your achievable bandwidth.