我想模仿ping,向一臺主機發送ICMP request,同時接受reply,但是卻阻塞在recvfrom上,不知為何,求解.
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netdb.h>
#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
/* My own ICMP structure */
struct myicmp
{
unsigned char icmp_type;
unsigned char icmp_code;
unsigned short icmp_cksum;
unsigned short icmp_id1;
unsigned short icmp_seq1;
};
/* argv[1] can be either hostname or IP address */
main(int argc, char *argv[])
{
struct sockaddr_in address;
u_char sendpack[32];
struct myicmp *icp;
int Nbytes, sock , status, buf_len;
struct sockaddr_in Current_Sockaddr;
char buffer[100];
struct hostent *host;
if (argc != 2)
{
printf("usage : %s <hostname|IP address>\n", argv[0]);
exit(1);
}
if ((host=gethostbyname((const char*)argv[1])) == NULL)
{
if ((address.sin_addr.s_addr = inet_addr(argv[1])) == -1)
{
printf("%s: unknown host\n", argv[1]);
exit(1);
}
}
else
{
bcopy(host->h_addr_list[0], &(address.sin_addr.s_addr),
host->h_length);
}
memset(sendpack, 0x0, sizeof(sendpack));
memset(buffer, 0x0, sizeof(buffer));
icp=(struct myicmp*)sendpack;
icp->icmp_type=ICMP_ECHO;
icp->icmp_code=0;
icp->icmp_seq1=1; /* any abritrary sequence number */
icp->icmp_id1=123; /* any arbitrary id */
address.sin_family = AF_INET;
/* 1 is for ICMP protocol : from /etc/protocols */
sock = socket(AF_INET,SOCK_RAW, 1);
buf_len = sizeof(buffer);
Nbytes= sendto(sock, (const void *)sendpack, sizeof(sendpack), 0,
(struct sockaddr *)&address,sizeof(address));
printf ("Data is sent to %s\n", inet_ntoa(address.sin_addr));
printf ("No of bytes sent = %d\n", Nbytes);
buf_len = sizeof(Current_Sockaddr );
Nbytes= recvfrom(sock, buffer, buf_len, 0,
(struct sockaddr *)&Current_Sockaddr, &buf_len );
printf ("Data received from %s\n", inet_ntoa(Current_Sockaddr.sin_addr));
/* get the sequence-id : First 20 bytes are for IP header :
21t byte is the sequence-id */
icp=(struct myicmp*)&buffer[20];
printf("Received sequence id is %d\n", icp->icmp_seq1);
printf ("No of bytes recd = %d\n", Nbytes);
}
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抓包看下，可能目標主機不可達？試一下127.0.0.1能不能收到包。轉載請註明出處，本文鏈接：https://www.uj5u.com/qita/142680.html
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