스레드로 만든 서버인데 자꾸 죽네요..

스레드로 간단 한 에코서버를 만들어 봤는데요..
여러 클라이언트가 접속후 데이타를 주고 받다가..
그중 하나의 클라이언드를 종료 하면 서버도
같이 죽네요...

뭐가 문제인지.......ㅠ.ㅠ

소스 올립니다..한번 봐주세요..

#include <sys/stat.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/file.h>
#include <stdio.h>
#include <sys/socket.h>
#include <strings.h>
#include <signal.h>
#include <netdb.h>
#include <time.h>

void *do_chld(void *);

int main(int argc, char *argv[]){
int server_sockfd, client_sockfd;
int state, client_len;
int pid;
int count=0;

struct sockaddr_in clientaddr, serveraddr;
pthread_t chld_thr;

char buf[255], line[255];
char szBuff[200];

if(argc != 2){
printf("사용법 : %s [port number]\n", argv[0]);
exit(0);
}

memset(szBuff, 0x00, sizeof(szBuff));
memset(line, 0x00, sizeof(line));
state = 0;

client_len = sizeof(clientaddr);
if( (server_sockfd = socket(AF_INET, SOCK_STREAM, 0) ) < 0){
perror("socket error : ");
exit(0);
}

bzero(&serveraddr, sizeof(serveraddr) );
serveraddr.sin_family = AF_INET;
serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
serveraddr.sin_port = htons(atoi(argv[1]) );

state = bind(server_sockfd, (struct sockaddr*)&serveraddr, sizeof(serveraddr));
if(state == -1){
perror("bind error : ");
exit(0);
}

state = listen(server_sockfd, 10);
if(state == -1){
perror("listen error : ");
exit(0);
}

signal(SIGCHLD, SIG_IGN);

while(1){
client_sockfd = accept(server_sockfd, (struct sockaddr*)&clientaddr, &client_len);
if(client_sockfd == -1){
perror("Accept error : ");
exit(0);
}
pthread_create(&chld_thr, NULL, do_chld, (void*)&client_sockfd);

}

close(client_sockfd);
}

void *do_chld(void *arg){
int client_sockfd = *((int*)arg);
char buf[255];

while(1){
memset(buf, '0x00', sizeof(buf));
if(read(client_sockfd, buf, 255) <= 0){
close(client_sockfd);
exit(0);
}
printf(": [%s]\n", buf);

write(client_sockfd, buf, 255);

}
}