Network, host machines sequence learning

Network, host machines sequence learning

Network, host machines sequence always stumbled. We need to sort out.
A thousand words, as the code to reality. Haha, I went ahead.

#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>

int host_order() 
{
    unsigned long a = 0x12345678;
    unsigned char * p = (unsigned char *)(&a);

    printf("主机字节序:%0x  %0x %0x %0x\n",p[0],p[1],p[2],p[3]);

    unsigned long b = htonl(a);

    p = (unsigned char *)(&b);

    printf("网络字节序:%0x  %0x %0x %0x\n",p[0],p[1],p[2],p[3]);

    return 0;
}

int net_order()
{
    struct in_addr ipaddr;
    unsigned long addr = inet_addr("192.168.1.100");
    unsigned char *p = (unsigned char *)(&addr);
    printf("addr = %u \n",addr);
    printf("%0x %0x %0x %0x : inet_addr 192.168.1.100\n",p[0],p[1],p[2],p[3]);
    printf("%d  %d  %d  %d : inet_addr 192.168.1.100\n",p[0],p[1],p[2],p[3]);
    unsigned long addr_host = ntohl(addr);
    p = (unsigned char *)(&addr_host);
    printf("%0x %0x %0x %0x : inet_addr ntohl 192.168.1.100\n",p[0],p[1],p[2],p[3]);
    printf("%d  %d  %d  %d : inet_addr ntohl 192.168.1.100\n",p[0],p[1],p[2],p[3]);
    printf("addr_host = %u\n",addr_host);
    return 0;
}

int main()
{
    int ret = 0;
    //ret = host_order();
    ret = net_order();
    return ret ;
}

Compile it.

gcc -g  -o test_order test_order.c

Running about.

[root@localhost test]# ./test_order                       
addr = 1677830336 
c0      a8 1    64 : inet_addr 192.168.1.100
192     168  1  100 : inet_addr 192.168.1.100
64      1 a8    c0 : inet_addr ntohl 192.168.1.100
100     1  168  192 : inet_addr ntohl 192.168.1.100
addr_host = 3232235876

Clear. It helps to quickly understand.