소켓 select 뭐가 문제일까요?

#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
 
#define SERV_TCP_PORT 
#define SERV_ADDR ""
 
void transfile(int s2);
void receivefile(int s2);
 
void main(){
   int s1,s2, x, y;
   struct sockaddr_in serv_addr, cli_addr;
   char buf[50];
   socklen_t  xx;
   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);
 
   //open a tcp socket
   if ((s1=socket(PF_INET, SOCK_STREAM, 0))<0){
      printf("socket creation error\n");
      exit(1);
   }
 
   // bind ip
 
   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);
   int i,k,f;
   char doit[50];
   char str[50];
 
  for(i; i<3; i++){
     s2 = accept(s1, (struct sockaddr *)&cli_addr, &xx);
     printf("we passed accept. new socket num is %d\n", s2);
 
     k = fork();
 
     if(k==0){
        printf("now connect with client %d \n", s2);
        printf("========================\n");
        y = read(s2, buf, 50);
        buf[y]=0;
        if(strcmp(buf, "hello")==0) {
           printf("successfull connect!\n");
           write(s2, "Type <download> or <upload>", 27);
           y= read(s2, doit, 50);
           doit[y] = 0;
           if(strcmp(doit, "download")==0) transfile(s2);
           else if(strcmp(doit, "upload")==0) receivefile(s2);
        }
        close(s2);
        close(s1);
        exit(0);
     }  //child do
     else {
        close(s2);
     }  //parent do
  }
  close(s1);   // close the original socket
}

void receivefile(int s2){
   struct timeval timeout;
   int x, y, cnt, rv;
   char fileName[50];
   char content[60];
   fd_set rset, temp;
   FD_ZERO(&rset);
   FD_ZERO(&temp);
   FD_SET(s2, &rset);
   timeout.tv_sec = 3;
   timeout.tv_usec = 0;
 
   printf("receivefile_mode\n");
   write(s2, "which file you want?", 20);
   y = read(s2, fileName, 50);
   fileName[y] = 0;
   printf("client : %s\n", fileName);
   x = open(fileName, O_RDWR | O_CREAT | O_TRUNC, 00777);
   if (x<0){
     write(s2, "protocol error", 20);
     close(y);
     return;
   }
 
   for(cnt; cnt<20; cnt++){
     printf("!!!!이 부분이 출력되지 않습니다!!!!\n");
     FD_SET(s2, &rset);
     temp = rset;
 
    /* upload */
     rv = select(s2+1, &temp, NULL, NULL, &timeout);
     if(rv==-1){
        perror("select");
     }
     else if(rv==0){
        break;
     }
     else {
        if(FD_ISSET(s2, &temp)){
          y = read(s2, content, 50);
          content[y] = 0;
          write(1, content, y);
          write(x, content, y);
        }
      }
   }
   printf("\n socket : %s done\n", s2);
}

#include "winsock2.h"
#include "ws2tcpip.h"
#include "stdio.h"
#pragma warning (disable : 4996)
#define SERVER_PORT 24680  // server port number
#define BUF_SIZE 4096 // block transfer size  
#define QUEUE_SIZE 10
#define IPAddress "165.246.38.151" // server IP address
 
void download(int s, int n, char buf[]);
void upload(int s, int n, char buf[]);
 
int main()
{
	WORD		        wVersionRequested;
	WSADATA		wsaData;
	SOCKADDR_IN          target; //Socket address information
	SOCKET		        s;
	int			err;
	int			bytesSent;
	char		        buf[100];
 
	//--- INITIALIZATION -----------------------------------
	wVersionRequested = MAKEWORD(1, 1);
	err = WSAStartup(wVersionRequested, &wsaData);
 
	if (err != 0) {
		printf("WSAStartup error %ld", WSAGetLastError());
		WSACleanup();
		return false;
	}
	//------------------------------------------------------
 
	//---- Build address structure to bind to socket.--------  
	target.sin_family = AF_INET; // address family Internet
	target.sin_port = htons(SERVER_PORT); //Port to connect on
	inet_pton(AF_INET, IPAddress, &(target.sin_addr.s_addr)); // target IP
															  //--------------------------------------------------------
 
 
															  // ---- create SOCKET--------------------------------------
	s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); //Create socket
	if (s == INVALID_SOCKET)
	{
		printf("socket error %ld", WSAGetLastError());
		WSACleanup();
		return false; //Couldn't create the socket
	}
	//---------------------------------------------------------
 
 
	//---- try CONNECT -----------------------------------------
	if (connect(s, (SOCKADDR *)&target, sizeof(target)) == SOCKET_ERROR)
	{
		printf("connect error %ld", WSAGetLastError());
		WSACleanup();
		return false; //Couldn't connect
	}
 
	//protocol test
	send(s, "hello", 5, 0);
 
	//recieve bytes from server
	int n;
	n = recv(s, buf, 50, 0);
	buf[n] = 0; // make a string
	printf("%s\n", buf);
 
	//---- SEND bytes -------------------------------------------
	gets_s(buf, 99);
	send(s, buf, strlen(buf), 0); // use "send" in windows
 
	if (strcmp(buf, "download") == 0) download(s, n, buf);
	else if (strcmp(buf, "upload") == 0) upload(s, n, buf);
	else {
		printf("protocol error");
		bytesSent = send(s, "protocol error try again", 20, 0);
	}
 
	//--------------------------------------------------------
	closesocket(s);
	WSACleanup();
 
	return 0;
}