Poll network programming for Linux/Unix Io multiplexing (including source code)

Preface

This section describes how to use basic Linux/Unix functions and poll calls to compile a complete server and client example that can be run on Linux (UBUNTU) and Unix (FreeBSD, the functions of the client and server are as follows:

The client reads a row from the standard input and sends it to the server.

The server reads a row from the network and then outputs the row to the client.

The client receives a response from the server and outputs this line to the standard output.

 

Server

CodeAs follows:

# Include <unistd. h>
# Include <sys/types. h> /*  Basic System Data Types  */ 
# Include <sys/socket. h> /*  Basic socket Definitions */ 
# Include <netinet/ In . H> /*  Sockaddr_in {} and other Internet defns  */ 
# Include <ARPA/inet. h> /*  INet (3) Functions  */ 

# Include <stdlib. h>
# Include <errno. h>
# Include <stdio. h>
# Include < String . H>


# Include <poll. h> /*  Poll Function  */ 
# Include <limits. h>

 # Define Maxline 10240

# Ifndef open_max
 # Define Open_max 40960
 # Endif 

 Void Handle ( Struct Pollfd * clients, Int Maxclient,Int Readyclient );

 Int Main ( Int Argc, Char ** Argv)
{
 Int Servport = 6888 ;
 Int Listenq = 1024 ;
 Int Listenfd, connfd;
 Struct Pollfd clients [open_max];
Int Maxi;
Socklen_t socklen = Sizeof ( Struct Sockaddr_in );
 Struct Sockaddr_in cliaddr, servaddr;
 Char Buf [maxline];
 Int Nready;

Bzero (& servaddr, socklen );
Servaddr. sin_family = af_inet;
Servaddr. sin_addr.s_addr = htonl (inaddr_any );
Servaddr. sin_port = htons (servport );

Listenfd = socket (af_inet, sock_stream, 0 );
 If (Listenfd < 0 ){
Perror ( "  Socket Error  " );
}

 Int Opt = 1 ;
 If (Setsockopt (listenfd, sol_socket, so_reuseaddr, & OPT, Sizeof (OPT) <0 ){
Perror ( "  Setsockopt Error  " );
}

 If (BIND (listenfd ,( Struct Sockaddr *) & servaddr, socklen) =- 1 ){
Perror ( "  BIND error  " );
Exit (- 1 );
}
 If (Listen (listenfd, listenq) < 0 ){
Perror ( "  Listen Error  " );
}

Clients [ 0 ]. FD = listenfd;
Clients [ 0 ]. Events = Pollin;
 Int I;
 For (I =1 ; I <open_max; I ++)
Clients [I]. FD =- 1 ;
Maxi = listenfd + 1 ;

Printf ( "  Pollechoserver startup, listen on port: % d \ n  " , Servport );
Printf ( "  Max connection is % d \ n  " , Open_max );

 For (;;){
Nready = poll (clients, Maxi + 1 ,- 1 );
 //  Printf ("nready is % d \ n", nready );  
          If (Nready =- 1 ){
Perror ( "  Poll Error  " );
}
 If (Clients [ 0 ]. Revents & Pollin ){
Connfd = accept (listenfd ,( Struct Sockaddr *) & cliaddr, & socklen );
Sprintf (BUF, "  Accept form % s: % d \ n  " , Inet_ntoa (cliaddr. sin_addr), cliaddr. sin_port );
Printf (BUF, "" );

 For (I = 0 ; I <open_max; I ++ ){
 If (Clients [I]. FD =-1 ){
Clients [I]. FD = connfd;
Clients [I]. Events = Pollin;
 Break ;
}
}

 If (I = open_max ){
Fprintf (stderr, "  Too connected connection, more than % d \ n  " , Open_max );
Close (connfd );
 Continue ;
}

 If (I> Maxi)
Maxi = I;

-- Nready;
}

Handle (clients, Maxi, nready );
}
}

 Void Handle ( Struct Pollfd * clients, Int Maxclient, Int Nready ){
 Int Connfd;
Int I, nread;
 Char Buf [maxline];

 If (Nready = 0 )
 Return ;

 For (I = 1 ; I <maxclient; I ++ ){
Connfd = clients [I]. FD;
 If (Connfd =- 1 )
 Continue ;
 If (Clients [I]. revents & (Pollin | pollerr )){
Nread = read (connfd, Buf, maxline ); //  Read client socket stream  
              If (Nread < 0 ){
Perror ( "  Read Error  " );
Close (connfd );
Clients [I]. FD =- 1 ;
Continue ;
}
 If (Nread = 0 ){
Printf ( "  Client close the connection  " );
Close (connfd );
Clients [I]. FD =- 1 ;
 Continue ;
}

Write (connfd, Buf, nread );//  Response Client  
              If (-- Nready <= 0 ) //  No connection to be processed, exit the loop  
                  Break ;
}
}
}

 

Download and compile

Compile and start the server

 
GCC pollechoserver. C-o pollechoserver
./Pollechoserver
 

For the client, refer to the echoclient example of the Linux/Unix server and client socket programming getting started instance in this article to download and compile.