What is the difference between a port address, a logical address and a physical address.

Port address: There are many applications running on the computer. Each application run with a port no (logically) on the computer. This port no for application is decided by the kernel of the OS. This port no is called port address. 

Logical Address: An IP address of the system is called logical address. This address is the combination of Net ID and Host ID. This address is used by network layer to identify a particular network among the networks. This address can be changed by changing the host position on the network. So it is called logical address.

Physical address: Each system having a NIC (Network Interface Card) through which two systems physically connected with each other with cables. The address of the NIC is called physical address or MAC address. This address is used by data link layer.