Global initialization of structure - visual-c++

Question

How can I initialize struct sockaddr_in globally. Third variable IN_ADDR sin_addr is a nested structure.
struct sockaddr_in{
short sin_family;
unsigned short sin_port;
IN_ADDR sin_addr;
char sin_zero[8];
} addr;
struct in_addr {
union {
struct { u_char s_b1,s_b2,s_b3,s_b4; } S_un_b;
struct { u_short s_w1,s_w2; } S_un_w;
u_long S_addr;
} S_un;
};

Answer 1

Point 1
You cannot initalize struct sockaddr_in itself. You need to have a variable of this type, i.e, addr (as in your case) which you can initialize.
Point 2
You can use an inilitalizer list in brace-enclosed form to initialize the global variable. Also, you can make use of the .identifier option to initalize a member explicitly.
Assuming IN_ADDR is defined as
typedef struct sockaddr_in IN_ADDR;
you can write something like
struct sockaddr_in{
short sin_family;
unsigned short sin_port;
IN_ADDR sin_addr;
char sin_zero[8];
} addr = {AF_INET, 2015, .sin_addr.S_un.S_addr = 1234567890, .sin_zero = {1,2,3,4,5,6,7}};
to initilialize addr.
Here, the .sin_addr.S_un.S_addr is used to denote to the particular variable to be initializeed.

Answer 2

Using your structure/union definition ... here is a sample program ...
#include <stdio.h>
typedef unsigned char u_char;
typedef unsigned short u_short;
typedef unsigned long u_long;
typedef struct in_addr
{
union
{
struct { u_char s_b1,s_b2,s_b3,s_b4; } S_un_b;
struct { u_short s_w1,s_w2; } S_un_w;
u_long S_addr;
}S_un;
}IN_ADDR;
IN_ADDR u = // ====> Either do something like this ...
{
.S_un.S_un_b = {'a', 'b', 'c', 'd'}
//.S_un.S_un_w = {1, 2},
//.S_un.S_addr = 121212
};
struct sockaddr_in
{
short sin_family;
unsigned short sin_port;
IN_ADDR sin_addr;
char sin_zero[8];
}addr = { // ==============> Or do something like this.
10,
20,
.sin_addr.S_un.S_addr=12345,
"SOCKET"
};
int main()
{
printf("sin_family = %d\n", addr.sin_family);
printf("sin_port = %d\n", addr.sin_port);
printf("sin_addr.S_un.S_addr = %ld\n", addr.sin_addr.S_un.S_addr);
printf("sin_zero = %s\n", addr.sin_zero);
printf("%c %c %c %c\n", u.S_un.S_un_b.s_b1, u.S_un.S_un_b.s_b2, u.S_un.S_un_b.s_b3, u.S_un.S_un_b.s_b4);
//printf("%d %d\n", u.S_un.S_un_w.s_w1, u.S_un.S_un_w.s_w2);
//printf("%ld\n", u.S_un.S_addr);
return 0;
}