About the relationship between async and multithreading

The personal understanding is this:

1. Asynchronous communication means that after a sends a message, it does not wait for a response from B to proceed with the execution of the program. At some point in the future, a will check to see if B's response is received.

Asynchronous is independent of each other, in the process of waiting for an event to continue to do their own things, do not have to wait for the event to complete and then work.

2. Multithreading is the logical layer concept of programming, which is a piece of code that runs concurrently in a process. Multithreading enables switching between threads to execute.

3. Asynchronous and synchronous are relative, synchronization is sequential execution, execution of one after execution of the next, need to wait, coordinated operation. A thread is a way to implement Asynchrony. Async is the main thread that lets the calling method do not need to wait for another thread to finish synchronously, so that the main thread can Cheng Gan other things.

Async and multithreading are not an equal relationship, asynchronous is the ultimate goal, multithreading is just a means for us to implement Asynchrony. Asynchronous is when a call request is sent to the callee, and the caller can do something else without waiting for the return of the result. The implementation of Asynchrony can be handled by multithreading or by handing it to another process.