socket 接收数据时出错（段错误）

大家好，又是我来问linux下socket问题了。我那个UPD的程序终于改好了，现在客户端跟服务器端都可以正常编译运行了。但是，问题又来了...
  我先运行服务器端，正常，再运行客户端向服务器端发送数据，这时服务器端就自动报错退出了，提示是段错误。请问是不是因为接受数据的内存区不为0造成的？请问应该怎么清空接收数据的内存区？谢谢

gdb看看core呀，看哪一句错了

代码如下，接收数据时就报错了


客户端

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>
#include <sys/socket.h>
#include <sys/wait.h>
#define MYPORT 4950 /* the port users will be sending to */

int main(int argc, char *argv[])
{
int sockfd;
struct sockaddr_in their_addr; /* connector's address information */
struct hostent *he;
int numbytes;
if(argc != 3)
{
   fprintf(stderr,"usage: talker hostname message\n";
   exit (1);
}

if((he=gethostbyname(argv[1])) == NULL)
{ /* get the host info */
   herror("get host by name" );
   exit(1);
}

if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
{
   perror("socket";
   exit( 1 );
}

their_addr.sin_family = AF_INET; /* host byte order */
their_addr.sin_port = htons(MYPORT); /* short, network byte order */
their_addr.sin_addr = *((struct in_addr *)he->h_addr);
bzero(&(their_addr.sin_zero), ; /* zero the rest of the struct */

if((numbytes=sendto(sockfd, argv[2], strlen(argv[2]), 0, (struct sockaddr *)&their_addr, sizeof(struct sockaddr))) == -1)
{
   perror("send to" );
   exit(1);
}

printf("sent %d bytes to %s\n",numbytes,inet_ntoa(their_addr.sin_addr));
close(sockfd);

return 0;
}

服务端:

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#define MYPORT 4950 /* the port users will be sending to */
#define MAXBUFLEN 100

main()
{
int sockfd;
struct sockaddr_in my_addr; /* my address information */
struct sockaddr_in their_addr; /* connector's address information */
int addr_len, numbytes;
char buf[MAXBUFLEN];

if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
{
   perror("socket" ;
   exit(1) ;
}
my_addr.sin_family = AF_INET; /* host byte order */
my_addr.sin_port = htons(MYPORT); /* short, network byte order */
my_addr.sin_addr.s_addr = INADDR_ANY; /* auto-fill with my IP */
bzero(&(my_addr.sin_zero), ; /* zero the rest of the struct */

if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1)
{
   perror( "bind " ) ;
   exit(1) ;
}

addr_len = sizeof(struct sockaddr);

if ((numbytes=recvfrom(sockfd, buf, MAXBUFLEN, 0, (struct sockaddr *)&their_addr, &addr_len)) == -1)
{
   perror( "recvfrom " ) ;
   exit(1) ;
}

printf("got packet from %s\n",inet_ntoa(their_addr. sin_addr)) ;
printf("packet is %d bytes long\n",numbytes);
buf[numbytes] = '\0';
printf("packet contains \"%s\"\n",buf);
close(sockfd);
}

struct sockaddr_in their_addr; /* connector's address information */
addr_len = sizeof(struct sockaddr);

两者结构不一样

sizeof(struct sockaddr))
改成sizeof(my_addr)