리눅스 tcp 소켓프로그램에서 bind()에러가 생겨요

/*
 * echo_server.c
 * Written by SW. YOON
 */
 
#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 IPADDR "127.0.0.1"
#define PORT 9190
 
#define BUFSIZE 1024
void error_handling(char *message);
 
int main(int argc, char **argv)
{
	int serv_sock;
	int clnt_sock;
	char message[BUFSIZE];
	int str_len;
 
	FILE *fp;
	int count =0;
	nSockOpt = 1;
 
	struct sockaddr_in serv_addr;
	struct sockaddr_in clnt_addr;
	int clnt_addr_size;
 
	serv_sock=socket(PF_INET, SOCK_STREAM, 0);   
	if(serv_sock == -1)
		error_handling("socket() error");
 
	memset(&serv_addr, 0, sizeof(serv_addr));
	serv_addr.sin_family=AF_INET;
	serv_addr.sin_addr.s_addr=inet_addr(IPADDR);
	serv_addr.sin_port=htons(PORT);
 
//bind()에러를 방지하는 함수라고 해서 추가했어요~
        setsockopt(nServSock, SOL_SOCKET, SO_REUSEADDR, &nSockOpt, sizeof(nSockOpt));
 
	if(bind(serv_sock, (struct sockaddr*) &serv_addr, sizeof(serv_addr))==-1)
		error_handling("bind() error");
 
	if(listen(serv_sock, 5)==-1)
		error_handling("listen() error");
 
	clnt_addr_size=sizeof(clnt_addr);    
	clnt_sock=accept(serv_sock, (struct sockaddr*)&clnt_addr,&clnt_addr_size);
	if(clnt_sock==-1)
		error_handling("accept() error");
 
	fp = fopen("packet.txt", "w");
 
	/* 데이터 수신 및 전송 */
	while( (str_len=read(clnt_sock,message, BUFSIZE)) != 0) {
		count++;
		write(clnt_sock, message, str_len);
		message[str_len]=0;
		fprintf(fp, " message : [%2d] %s \n", count, message);
	}
 
	fclose(fp);
 
	close(clnt_sock);
	return 0;
}
 
void error_handling(char *message)
{
	fputs(message, stderr);
	fputc('\n', stderr);
	exit(1);
}

/*
 * echo_client.c
 * Written by SW. YOON
 */
 
#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 IPADDR "127.0.0.1"
#define PORT 9190
 
#define BUFSIZE 1024
void error_handling(char *message);
 
int main(int argc, char **argv)
{
	int sock;
	char message[BUFSIZE]="Hello packet";
	int str_len;
	struct sockaddr_in serv_addr;
 
	int count =0;
 
	sock=socket(PF_INET, SOCK_STREAM, 0);   
	if(sock == -1)
		error_handling("socket() error");
 
	memset(&serv_addr, 0, sizeof(serv_addr));
	serv_addr.sin_family=AF_INET;
	serv_addr.sin_addr.s_addr=inet_addr(IPADDR);
	serv_addr.sin_port=htons(PORT);
 
	if(connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr))==-1)
		error_handling("connect() error!");
 
	while(1) {
		if(count >=1000) break;
		count ++;
 
		if(!strcmp(message,"q\n"))	break;
		write(sock, message, strlen(message));
 
		/* 메세지 수신, 출력 */
		str_len=read(sock, message, BUFSIZE-1);
		message[str_len]=0;
		printf("recv message from server : [%2d] %s \n", count, message);
	}
 
	close(sock);
	return 0;
}
 
void error_handling(char *message)
{
	fputs(message, stderr);
	fputc('\n', stderr);
	exit(1);
}