Question

I have programed a server-client application as a RPC (low-level).

This is my server function to validate my IP address (here, just the necessary information):

 int *checkip_1_svc(ip_adress *argp, struct svc_req *rqstp)
 {
     static int  result;
     struct sockaddr_in test_ip;

     result =1;

     return(&result);
 }

Now I want to print the IP address from the connected client.

I tried:

printf("Clientadress:%s", rqstp->rq_xprt->xp_raddr.sin_addr.s_addr);

This does not work. I get a segmentation fault.

Answer 1

s_addr most propably is an unsigned 32bit integer, so you might use %u but %s:

printf("client address: %u", rqstp->rq_xprt->xp_raddr.sin_addr.s_addr);

To have it printed in the a.b.c.d notation you might use:

#define SPLIT_S_ADDR_INTO_BYTES( \
    s_addr) \
    ((s_addr) >> 24) & 0xFF, \
    ((s_addr) >> 16) & 0xFF, \
    ((s_addr) >>  8) & 0xFF, \
    ((s_addr)      ) & 0xFF

...

printf(
  "client address: %hu.%hu.%hu.%hu", 
  SPLIT_S_ADDR_INTO_BYTES(ntohl(rqstp->rq_xprt->xp_raddr.sin_addr.s_addr)));

...

For details on ntohl() please see man ntohl().