Linux Network Programming-non-blocking programming

Introduction to the design of non-blocking methods

The most significant difference between the non-blocking operation and the blocking mode is that the function's call returns immediately, regardless of whether the data was successfully read or successfully written. You can do non-blocking programming by using FCNTL () to set the socket file descriptor following code:
Fcntl (S, F_SETFL, O_nonblock);
where S is the socket file descriptor, using the F_SETFL command to set the socket s to non-blocking mode, and then read and write operations can be returned immediately.

Examples of non-blocking programming

The function accept () can use a non-blocking way to poll waiting for the arrival of the client before setting the Non_block mode. The following code uses polling to use the Accept () and recv () functions, when the client sends a "HELLO" string, sends an "OK" response to the client and shuts down the client, and when the client sends the "SHUTDOWN" string to the server, the server sends the "BYE" client, And close the client, and then quit the program.

#define PORT 9999#Define BACKLOG 4intMainintargcChar*argv[]) {structSockaddr_in local,client;intLenints_s =-1, s_c=-1;/ * Initialize the address structure * /Bzero (&local,sizeof(local));/ * Clear 0 * /Bzero (&client,sizeof(client));/ * Clear 0 * /local.sin_family = af_inet;    Local.sin_port = htons (port); LOCAL.SIN_ADDR.S_ADDR = htonl (-1);/ * Create a Socket descriptor * /s_s = socket (af_inet, Sock_stream,0);/ * Set non-blocking mode * /Fcntl (S_S,F_SETFL, O_nonblock);/ * Listen * /Listen (s_s, BACKLOG); for(;;) {/* Poll the receiving client * /         while(S_c <0){/ * Wait for client to arrive * /S_c =accept (s_s, (structsockaddr*) &client, &len); }/ * Polling for receive, exiting while loop when data is received * /         while(Recv (s_c, buffer,1024x768) <=0)            ;/ * Receive the client's data * /        if(strcmp (Buffer,"HELLO")==0){/ * Determine if it is a hello String * /Send (S,"OK",3,0);/ * Send response * /Close (S_c);/ * Close connection * /            Continue;/ * Continue waiting for Client connection * /}if(strcmp (Buffer,"SHUTDOWN")==0){/ * Determine if the string is shutdown * /Send (S,"BYE",3,0);/ * Send bye String * /Close (S_c);/ * Close the Client connection * /             Break;/ * Exit main loop * /}} close (s_s);return 0;}

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Linux Network Programming-non-blocking programming