网站空间ip查询,汕头澄海地图,wordpress 显示错误,设计配色推荐的网站现在进入第二步#xff0c;捕获数据包。从第20行开始#xff0c;我们进入了一个死循环#xff0c;while(1)#xff0c;在第24行#xff0c;recvfrom(sock, buffer, sizeof buffer, 0, (struct sockaddr *)from, fromlen)#xff0c;这个函数要做的就是接收数据…现在进入第二步捕获数据包。从第20行开始我们进入了一个死循环while(1)在第24行recvfrom(sock, buffer, sizeof buffer, 0, (struct sockaddr *)from, fromlen)这个函数要做的就是接收数据冰把接收到的数据放入buffer中。就是这么简单已经完成了我们要捕获数据包的任务。到了第三步分析数据包。27行ip (struct ip *)buffer使我们在头文件中的IP结构对应于所接收到的数据接下来判断在网络层中是否使用的是TCP协议if(ip- ip_protocol 6) 如果答案是tcp信息包从整个IP/TCP包 buffer (4*ip- ip_length) 地址处开始所以31行 tcp (struct tcp *)(buffer (4*ip- ip_length))然后对应结构把你所需要的信息输出。/*************************headers.h**************************//*structure of an ip header*/struct ip {unsigned int ip_length:4; /*little-endian*/unsigned int ip_version:4;unsigned char ip_tos;unsigned short ip_total_length;unsigned short ip_id;unsigned short ip_flags;unsigned char ip_ttl;unsigned char ip_protocol;unsigned short ip_cksum;unsigned int ip_source; unsigned int ip_dest;};/* Structure of a TCP header */struct tcp {unsigned short tcp_source_port;unsigned short tcp_dest_port;unsigned int tcp_seqno;unsigned int tcp_ackno;unsigned int tcp_res1:4, /*little-endian*/tcp_hlen:4,tcp_fin:1,tcp_syn:1,tcp_rst:1,tcp_psh:1,tcp_ack:1,tcp_urg:1,tcp_res2:2;unsigned short tcp_winsize;unsigned short tcp_cksum;unsigned short tcp_urgent;};/*********************EOF***********************************/另外一个例子#include #include #include #include #include #include #include int main(int argc, char **argv){int sock, n;char buffer[2048];unsigned char *iphead, *ethhead;if ( (socksocket(PF_PACKET, SOCK_RAW,htons(ETH_P_IP))) 0){perror( socket );exit(1);}while (1) {printf( ----------\n );n recvfrom(sock,buffer,2048,0,NULL,NULL);printf( %d bytes read\n ,n);/* Check to see if the packet contains at least* complete Ethernet (14), IP (20) and TCP/UDP* (8) headers.*/if (n 42) {perror( recvfrom(): );printf( Incomplete packet (errno is %d)\n ,errno);close(sock);exit(0);}ethhead buffer;printf( Source MAC address: %02x:%02x:%02x:%02x:%02x:%02x\n ,ethhead[0],ethhead[1],ethhead[2],ethhead[3],ethhead[4],ethhead[5]);printf( Destination MAC address: %02x:%02x:%02x:%02x:%02x:%02x\n ,ethhead[6],ethhead[7],ethhead[8],ethhead[9],ethhead[10],ethhead[11]);iphead buffer14; /* Skip Ethernet header */if (*iphead0x45) { /* Double check for IPv4* and no options present */printf( Source host %d.%d.%d.%d\n ,iphead[12],iphead[13],iphead[14],iphead[15]);printf( Dest host %d.%d.%d.%d\n ,iphead[16],iphead[17],iphead[18],iphead[19]);printf( Source,Dest ports %d,%d\n ,(iphead[20] 8)iphead[21],(iphead[22] 8)iphead[23]);printf( Layer-4 protocol %d\n ,iphead[9]);}}
