fopen返回NULL
以下是代码
求解为什么会fopen返回NULL;
#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#define TURE 1
#define LOCAL_SERVER_PORT 5866
#define MAX_MSG 1024
int main(void)
{
int n, fd;
socklen_t cli_addr_len;
char buf[MAX_MSG] = {0};
unsigned long int npak=0;
struct sockaddr_in servaddr, cliaddr;
FILE *fp;
int KZ=0;
int sendbufsize,recvbufsize;
int size=4;
printf("n%20 printf or 1 printf or no printf(2/1/0)?");//多少个包打印一次
scanf("%d", &KZ);
printf("stat:\n");
if((fp=fopen("udp.dat", "wb")) == NULL)
{
printf("error - open file.");
return 0;
}
if((fd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
{
printf("socket error!\n");
exit(0);
}
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(LOCAL_SERVER_PORT);
bind(fd, (struct sockaddr *)&servaddr, sizeof(servaddr));
//设置系统缓冲区大小
size = sizeof(int);
recvbufsize = 0;
if(getsockopt(fd, SOL_SOCKET, SO_RCVBUF, (void *)&recvbufsize, &size) == 0)
printf("recvbufsize = %d\n", recvbufsize);
recvbufsize = 128*1024;
if(setsockopt(fd, SOL_SOCKET, SO_RCVBUF, (void *)&recvbufsize, sizeof(int)) == 0 )
printf("recvbufsize = %d\n", recvbufsize);
if(getsockopt(fd, SOL_SOCKET, SO_RCVBUF, (void *)&recvbufsize, &size) == 0)
printf("recvbufsize = %d\n", recvbufsize);
while(TURE)
{
cli_addr_len = sizeof(cliaddr);
n =recvfrom(fd, buf,MAX_MSG, 0, (struct sockaddr *)&cliaddr, &cli_addr_len);//接收数据
npak++;
if((KZ==2) && !(npak%20))
printf("%d\n", npak);
else if(KZ == 1)
printf("%d\n", npak);
fwrite(buf, MAX_MSG, 1, fp);//写硬盘,每一个包一写
}
fclose(fp);
return 0;
}