소켓// 블럭 논블럭 read()에 대해서

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <sys/time.h>
#include <unistd.h>
#include <sys/select.h>
 
#define SERV_TCP_PORT 
#define SERV_ADDR ""
 
struct client{
      char name[20];  // this client's name
      int state;      // state
      int partner;    // socket number of talking partner
};
 
void handle_protocol(int x, fd_set * pset, struct client* cli);
 
void main(){
   int s1,s2, i, x, y;
   int stateToZero;
   struct sockaddr_in serv_addr, cli_addr;
   char buf[50];
   struct client cli[50];
   socklen_t  xx;
 
   for(stateToZero; stateToZero<50; stateToZero++){
      cli[stateToZero].state = 0;
   }
   printf("Hi, I am the server\n");
 
   bzero((char *)&serv_addr, sizeof(serv_addr));
   serv_addr.sin_family=PF_INET;
   serv_addr.sin_addr.s_addr=inet_addr(SERV_ADDR);
   serv_addr.sin_port=htons(SERV_TCP_PORT);
 
 
   if ((s1=socket(PF_INET, SOCK_STREAM, 0))<0){
      printf("socket creation error\n");
      exit(1);
   }
   printf("socket opened successfully. socket num is %d\n", s1);
 
 
   x =bind(s1, (struct sockaddr *)&serv_addr, sizeof(serv_addr));
   if (x < 0){
      printf("binding failed\n");
      exit(1);
   }
   printf("binding passed\n");
   listen(s1, 5);
   xx = sizeof(cli_addr);
 
   fd_set rset, pset;
   int maxfd=50;
 
   FD_ZERO(&rset);
   FD_ZERO(&pset);
 
 
   FD_SET(s1, &pset);
      for(i=0;i<20;i++){       rset=pset; 
      select(maxfd, &rset, NULL, NULL, NULL);
      for(x=0;x<maxfd;x++){
         if (FD_ISSET(x, &rset)){ 
               if (x==s1){               
               s2 = accept(s1, (struct sockaddr *)&cli_addr, &xx);
               cli[s2].state = 1;
               printf("new cli at socket %d\n",s2);
               FD_SET(s2, &pset); 
            }else{ 
               handle_protocol(x, &pset, cli);
            }
         }
      }
   }
}

int y, cnt;
char buf[50];
y=read(x, buf, sizeof(buf)-1);
buf[y]=0;
 
for(cnt; cnt<10; cnt++){
   write(x, (cli+cnt)->name, strlen((cli+cnt)->name));
}

   ....
 
 
 
   printf("======LIST=====\n");
   for(;;){
      y=read(x, buf, 50);
      if(y==0) break;
      write(1, buf, y);
      printf("\n");
   }
   printf("===============\n");
 
 
   ....