Arm Mbed OS support forum

Getting ip address from mbedtls_net_accept

I was trying to get the client address by modifying the dtls example code.
However, I always get the 0.0.0.0 did I do anything wrong?

if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd,
client_ip, sizeof( client_ip ), &cliip_len ) ) != 0 )
{
printf( " failed\n ! mbedtls_net_accept returned %d\n\n", ret );
goto exit;
}
unsigned char bytes[4];
bytes[0] = *client_ip & 0xFF;
bytes[1] = (*client_ip >> 8) & 0xFF;
bytes[2] = (*client_ip >> 16) & 0xFF;
bytes[3] = (*client_ip >> 24) & 0xFF;
printf("%d.%d.%d.%d\n", bytes[3], bytes[2], bytes[1], bytes[0]);

HI @fire010g
Thank you for your interest in Mbed TLS.

All you need to do is get the bytes in client_ip(for IPv4):

printf("%d.%d.%d.%d\n", client_ip[0], client_ip[1], client_ip[2], client_ip[3]);

Note that client_ip is a byte array, so *client_ip will return client_ip[0], and then shifting it will always return 0. client_ip[0] is probably 0 in your case.
If you wish to use bitwise operation, for portability to different architectures, please try the following:

bytes[0] = *(uint32_t*)client_ip & 0xFF;
bytes[1] = (*(uint32_t*)client_ip >> 8) & 0xFF;
bytes[2] = (*(uint32_t*)client_ip >> 16) & 0xFF;
bytes[3] = (*(uint32_t*)client_ip >> 24) & 0xFF;

Regards,
Mbed TLS Support
Ron

Oh god, turns out example program using IPV6 instead of IPV4, after enable FORCE_IPV4 I can get the correct IP address.

1 Like

I’ve just been through this myself, and the best portable code for getting the address in text format is;

#include <arpa/inet.h>

    int err;
    mbedtls_net_context socket;
    char addr[16];
    size_t len;
    char ip[INET6_ADDRSTRLEN];

    if ((err=mbedtls_net_accept(&server->socket, &socket, addr, sizeof(addr), &len)))
        return err;
    if (!inet_ntop(len == 4 ? AF_INET : AF_INET6, addr, ip, sizeof(ip)))
        strcpy(ip, "<unknown>");

This will work for IPv4 and IPv6 addresses.