Full and half duplex, synchronous and asynchronous

Synchronous and asynchronous:

Because

Synchronize: Submit request, wait for server processing, and then return
Asynchronous: Requests are processed through event triggering server processing (which is still something the browser can do)

Also

Synchronization refers to: After the sender sends the data, wait for the receiver to send back the response , only send the next packet communication mode.
Asynchronous means that after the sender sends out the data, the receiver sends back the response , and then the next packet is communicated.

So

Synchronization is blocking mode, and asynchronous is non-blocking mode.

Simplex, full duplex and half duplex:

Simplex: Refers to the way messages can only be transmitted in one Direction

Half-duplex: refers to the data can be transmitted in two directions , but at the same time a channel only allows single-direction transmission , it is also known as bidirectional alternating communication

Full duplex: Refers to the simultaneous transmission of A to B and B to a on the line at any moment of communication

Full and half duplex, synchronous and asynchronous