The TCP/IP protocol is designed such that each computer or device in a network has a unique IP Address and each
IP address can open and communicate over up to 65535 different ports for sending and receiving data to or from any other network device.
The IP address uniquely identifies the computer or device on the network and a port number identifies a specific connection between one computer or device and another (i.e between two IP Addresses).
A TCP/IP port can be thought of as a private two-way communications line where the port number is used to identify a unique connection between two devices.
The concept is very similar to any other type of port on your PC (serial, parallel, etc) except that instead of having a physical connection, the TCP/IP protocol creates a
virtual IP port and the network hardware and software is responsible for routing data in and out of each virtual IP port.
User sends a file from Point A to Point B TCP IP slices the files into chunks or packets. TCP IP assigns each packet a number. The numbers are sequential to facilitate reassembly later on. The file travels sliced in packets TCP IP counts the number of packets and reassembles the file before delivery. If the file is missing a packet, TCP IP has it re-sent If the file looks exactly as it did when it was sent, it is delievered to Point B.