I want to imitate the ping, send ICMP request to a host, at the same time accept the reply, but block on the recvfrom, somehow, solving.

 # include & lt; Sys/types. H> 
#include  
#include  
#include  
#include  
#include  
#include  
#include  

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 the hostname or IP address */
The main (int arg c, 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 (arg c! 
=2){
Usage: printf (" % s & lt; The 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); 
} 
} 
The else 
{
Bcopy (host - & gt; H_addr_list [0], & amp; (address. Sin_addr. S_addr), 
The host - & gt; H_length); 
} 

Memset (sendpack, 0 x0, sizeof (sendpack)); 
Memset (buffer, 0 x0, sizeof (buffer)); 

Icp=(struct myicmp *) sendpack; 

Icp - & gt; Icmp_type=ICMP_ECHO; 
Icp - & gt; Icmp_code=0; 
Icp - & gt; Icmp_seq1=1;/* any abritrary sequence number */
Icp - & gt; Icmp_id1=123;/* any arbitrary id */

Address. Sin_family=AF_INET; 

/* 1 is for ICMP protocol: the from/etc/separate protocols */
The sock=socket (AF_INET SOCK_RAW, 1); 

Buf_len=sizeof (buffer); 
Nbytes=sendto (sock, (const void *) sendpack, sizeof (sendpack), 0, 
(struct sockaddr *) & amp; Address, sizeof (address)); 

Printf (" the 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 *) & amp; Current_Sockaddr, & amp; 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: 
21 t byte is the sequence id */
Icp=(struct myicmp *) & amp; Buffer [20]. 
Printf (" Received sequence id is % d \ n ", icp - & gt; Icmp_seq1); 

Printf (" No of bytes recd=% d \ n ", Nbytes); 
} 

CodePudding user response:

Caught a look, it may be a target host unreachable? Try 127.0.0.1 can receive the package,