tcpdump 抓不到包

[jianjian_qingdao]

小弟初学网络编程，想用tcpdump抓包看一下，但是死活抓不到，求大神指点
服务器代码

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <netinet/in.h>

#define SERVER_PORT 8003
#define MSG_BUF_SIZE 128

main()
{
int sockfd;
struct sockaddr_in my_addr;
struct sockaddr_in their_addr;
int addr_len,numbytes;
char buffer[MSG_BUF_SIZE];

if((sockfd = socket(AF_INET,SOCK_DGRAM,0)) == -1)
{
fprintf(stderr,"socket error");
exit(1);
}
my_addr.sin_family = AF_INET;
my_addr.sin_port = htons(SERVER_PORT);
my_addr.sin_addr.s_addr = INADDR_ANY;
bzero(&(my_addr.sin_zero),8);

if(bind(sockfd,(struct sockaddr *)&my_addr,sizeof(struct sockaddr)) == -1)
{
fprintf(stderr,"bind error\n");
exit(1);
}

addr_len = sizeof(struct sockaddr);

if((numbytes = recvfrom(sockfd,buffer,MSG_BUF_SIZE,0,(struct sockaddr *)&their_addr,&addr_len)) == -1)
{
fprintf(stderr,"recvfrom error");
exit(1);
}

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

客户端代码：
#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 SERVER_PORT 8003
int main(int argc,char *argv[])
{
int sockfd;
struct sockaddr_in their_addr;
struct hostent *hostname;
int num_bytes;

if(argc != 3)
{
fprintf(stderr,"usage:talker hostname message\n");
exit(1);
}
if((hostname = gethostbyname(argv[1])) == NULL)
{
fprintf(stderr,"gethostbyname");
exit(1);
}
if((sockfd = socket(AF_INET,SOCK_DGRAM,0)) == -1)
{
fprintf(stderr,"socket");
exit(1);
}

their_addr.sin_family = AF_INET;
their_addr.sin_port = htons(SERVER_PORT);
their_addr.sin_addr = *((struct in_addr *)hostname->h_addr);
bzero(&(their_addr.sin_zero),8);

if((num_bytes = sendto(sockfd,argv[2],strlen(argv[2]),0,(struct sockaddr *)&their_addr,sizeof(struct sockaddr))) == -1)
{
fprintf(stderr,"sendto");
exit(1);
}
printf("sent %d bytes to %s\n",num_bytes,inet_ntoa(their_addr.sin_addr));
close(sockfd);
return 0;
}
所用的命令是 tcpdump port 8003
程序正常运行，但是抓不到包

[jianjian_qingdao]

自己顶

[jianjian_qingdao]

怎么没人呢

[jianjian_qingdao]

坐等大神阿

[qq120848369]

本地环回不跑以太网卡，tcpdump -i lo 抓本地环回的。

[jianjian_qingdao]

哦，这样阿，太感谢拉，郁闷拉一上午

[阿斯顿撒旦撒旦撒]

看来你对tcpdump一点儿也不懂。给你推荐个博文。 http://blog.csdn.net/nibzer/article/details/38469155