Download Jperf from here.
To check the network speed between two machines, Jperf should be present on both the machines.
You can either run the jperf.bat or jperf.sh depending on your OS.
Suppose you want to test network speed between machine A and machine B.
Run machine A as client and machine B as server or vice versa.
On the machine running jperf as client enter the port address of the machine configured as jperf server.
Also note that use the port number you have set in the GUI of jperf server machine to be listening.