5-1 blocking / non blocking, synchronous / asynchronous

Blocking / Non blocking 、 Sync / asynchronous

A typical time IO What are the two stages of ？ Data ready and Data reading and writing

Data ready ： According to the system IO Ready state of the operation

Blocking
Non blocking

Data reading and writing ： Depending on how the application interacts with the kernel

Sync
asynchronous

Sync ： After function call , After getting the program result , Immediately proceed （ It takes the time of the program ）;
Example ： Buy air tickets , Take a taxi to the airport to get your ticket （ This action takes your own time ）;
Programming is relatively simple ;

asynchronous ： asynchronous IO Interface （sockfd,buf, Inform the way （ It's usually sigio The signal ））, Need notification , Don't wait for the program to call the function to return the result , Wait for the operating system （ kernel ） Put data into buf In , Notify the program to process the result of the function call ;
Example ： After buying the ticket , The courier will send the ticket from the airport to his home （ It takes someone else's time ）

A typical network IO Interface call , There are two stages , Namely “ Data ready ” and “ Data reading and writing ”, The data ready phase is divided into blocking and non blocking , The result is , Block the current thread or return directly .

Synchronization means A towards B Request to call a network IO Interface （ Or call some business logic API Interface ）, The data is read and written by the requestor A Do it yourself （ Whether it's blocked or not ）; Asynchronous representation A towards B Request to call a network IO Interface （ Or call some business logic API Interface ）, towards B The event of the incoming request and the way of notification when the event occurs ,A You can handle other logic , When B After listening to the completion of event processing , Will be notified in advance , notice A Processing results .

Blocking / Non blocking 、 Sync / Asynchronous instance