[ Foro de C ]

Listado de sockets que no se entiende muy bien

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/wait.h>

#define buffersize 1024


void sig_fork(int signo) {
   int stat;
   waitpid(0, &stat, WNOHANG);
   return;
}

int main(){
   signal(SIGCHLD, sig_fork);

   struct timeval timeout;
   timeout.tv_sec = 5; // sec
   timeout.tv_usec = 0; // ms


   int serv_sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
   struct sockaddr_in serv_addr;
   memset(&serv_addr, 0, sizeof(serv_addr));
   serv_addr.sin_family = AF_INET;  
   serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");  
   serv_addr.sin_port = htons(5566);  
   bind(serv_sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr));

   listen(serv_sock, 20);

   struct sockaddr_in clnt_addr;
   socklen_t clnt_addr_size = sizeof(clnt_addr);

   while (1) {
     int clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_addr, &clnt_addr_size);
     // set recv and send timeout
     if( setsockopt (clnt_sock, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout, sizeof(timeout)) < 0 )
       printf( "setsockopt fail\n" );
     if( setsockopt (clnt_sock, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout, sizeof(timeout)) < 0 )
       printf( "setsockopt fail\n" ) ;
     
     int pid = fork();
     if (pid == -1) {
       printf( "ERROR pid\n" );
     }
     
     else if (pid == 0) {
       printf("%d\n", getpid()) ;
       char *buffer = (char*) calloc(buffersize, sizeof(char));
       recv(clnt_sock, buffer, buffersize, 0) ;
       printf("Server receive:%s\n", buffer) ;
       int total = (int)(atoi(buffer)*atoi(buffer)) ;
       printf("Server return num^2:%d\n", total) ;
       char *returnvalue = (char*) calloc(buffersize, sizeof(char));
       sprintf( returnvalue, "result:%d", total ) ;
       send(clnt_sock, returnvalue, buffersize, 0) ;
       close(clnt_sock) ;
       close(serv_sock) ;
       return 0 ;
     }
     else {
       close(clnt_sock);
     }

   }    
     
   close(serv_sock);
   return 0;
}


No entiendo este código de pogramación de sockets, profesor haga el favor de explicarlos