Multiplexing IO model---epoll

Table of contents

1. Historical positioning

2. Interface

1. Create

int epoll_create(int size);

2. Operation:

int   epoll_ctl(int epfd, int  op,  struct  epoll_event  *event)

3. Wait:

        int  epoll_wait (int epfd,  struct  epoll_event  *events, int  maxevents , int  timeout);

3. The working principle of epoll

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1. Historical positioning

So far, the IO multiplexing model with the best performance on the linux platform. none of them.

2. Interface

1. Create

int epoll_create(int size);

size : It is currently deprecated, but for backward compatibility, you need to pass a number greater than 0 to size

 What is the meaning of epoll_create?

 

 Return value: epoll operation handle

With the operation handle, you can manipulate the created structure eventpoll

2. Operation:

int   epoll_ctl(int epfd, int  op,  struct  epoll_event  *event)

parameter:

epfd :    epoll operation handle

op:      options, through different ops, tell the epoll_ctl function what to do

• EPOLL_CTL_ADD
• Add an event structure corresponding to a file descriptor to epoll
• EPOLL_CTL_MOD
• Modify the event structure of a file descriptor
• EPOLL_CTL_DEL
• Delete the event structure corresponding to a file descriptor from epoll

fd:   the file descriptor to be processed (add, modify, delete), this fd is to tell the epoll_ctl function

event:   event structure in epoll

The events in the event structure event corresponding to the file descriptor are the events we want to care about. If there are multiple events at the same time, we also use or to connect.

return value:

        0 is normal.

        -1 for failure.

3. Wait:

        int  epoll_wait (int epfd,  struct  epoll_event  *events, int  maxevents , int  timeout);

parameter:

epfd :

        The operation handle of epoll

events :

        Event structure array (collection), get the ready event structure from epoll

maxevents :

        Maximum number of event structures to fetch at one time

timeout :

• >0 : with timeout event
• ==O: non-blocking
• <0: blocking

3. The working principle of epoll

Four, epoll simple server multi-channel transfer server

Here we can first encapsulate a tcp class for the server to provide tcp services for the server.

 Then let's implement an epoll monitoring

Let's verify it:

When we run the code, we can see that multiple clients connect to the server and send messages to it, and the server can receive it.