Internet Protocol (IP) defines a delivery of data from one network node to another. However, he does not guarantee the accuracy of delivery: packets in transit can be lost or not arrive in the order in which they were sent. Responsible for the accuracy the Protocol, the TRANSporttion level Transmission Control Protocol TCP. TCP establishes a connection, controls sending and receiving packets, duplicate their actions in that case, if the reply is not received or packets lost. It is important to understand that TCP sets the packet exchange, not just between nodes, and between software applications. The network port is a relative concept, a number from 1 to 65535 that specifies which application is assigned to the package.
To know what processes are used ports on your computer, you can use standard Windows tools. In the menu "start" click "run" and command prompt type cmd. Confirm with OK. In the console window type the command netstat -a-n-o.
In the PID column shows the number of the process in the column "Local address"is the IP address of your computer, a colon, the port number, which is busy with the appropriate process. "External address" is the IP and the port number of the remote host which is running some application.
In the console window type the command tasklist. It will return a list of all applications with ID PID running on the computer. So you learn, what process occupies any port on your computer.
Can obtain this information otherwise: run "task Manager" from the command line by typing taskmgr, or Ctrl+Alt+Delete. In the PID column find the number you are interested in process, in the column "image Name" – the name of the corresponding application or service. If PID is not displayed in the Manager window, go to "View" main menu and select the option "Choose columns". Tick the checkbox next to "Ref.the PID (process identifier)".