Socket 프로그래밍 질문이 있습니다..

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<arpa/inet.h>
#include<sys/types.h>
#include<sys/socket.h>
 
#define MAXLINE 511
 
int main(int argc, char *argv[])
{
        struct sockaddr_in servaddr, cliaddr;
 
        int s;
        int nbyte;
        int addrlen = sizeof(struct sockaddr);
 
        char buf[MAXLINE+1];
 
        if(argc != 2)
        {
                printf("Usage : %s port_number \n", argv[0]);
                exit(0);
        }
 
        if((s = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
        {
                perror("socket fail");
                exit(0);
        }
 
        bzero((char *)&servaddr, addrlen);
        bzero((char *)&cliaddr, addrlen);
 
        servaddr.sin_family = AF_INET;
        servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
        servaddr.sin_port = htons(atoi(argv[1]));
 
        if(bind(s, (struct sockaddr *)&servaddr, addrlen) < 0)
        {
                perror("bind Error");
                exit(0);
        }
 
        while(1)
        {
                puts("SERVER : WAITING REQUEST .... ");
                nbyte = recvfrom(s, buf, MAXLINE, 0, (struct sockaddr*)&cliaddr, &addrlen);
                if(nbyte < 0)
                {
                        perror("recvfrom fail");
                        exit(1);
                }
                buf[nbyte] = 0;
 
                <b>printf("%d:%d\n", cliaddr.sin_addr.s_addr, cliaddr.sin_port);</b>
                printf("%d byte recv : %s \n", nbyte, buf);
 
                if(sendto(s, buf, nbyte, 0, (struct sockaddr*)&cliaddr, addrlen) < 0)
                {
                        perror("sendto fail");
                        exit(1);
                }
                puts("sendto complete!");
        }
}