Raspbian C ++错误：“结构”之前的预期主表达式

Question

I am trying to write a program for my raspberry pi that changes its system time to the time from a GPS unit on the same network. The GPS sends out a 72 byte UDP packet across port 3000. I am new to socket programming so I am unsure where I am going wrong.

The trouble that I am having is that I can't seem to get it to build with g++. I am getting the following error:

So the main error seems to be in the line

char A = struct sockaddr_in address;

Here is the start of my program and the method where I create the socket and where the error is located, if you would like the main method of my program then I will add it too.

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <sys/time.h>
#include <errno.h>
#include <math.h>

// defines the socket used by the GPS
#define PORT 3000 

/****************************/
 int CreateSocket(int port)
/****************************/
{
    // Create an UDP-socket
    int sock = socket(AF_INET, SOCK_DGRAM, 0);

    // Check if UDP-socket was created
    if(sock==-1)
    {
       fprintf(stderr, "1CreateSocket: socket failed\n");
       return -1;
    }

    // Bind it to the local IP-address
    struct sockaddr_in address;
    char A = struct sockaddr_in address;
    fprintf(stderr, A);

    // Pointer to the block of memory to fill with address data
    memset(&address, 0, sizeof(address));

    address.sin_family      = AF_INET;             // Address family for IP-address 
    address.sin_addr.s_addr = htonl(INADDR_ANY);   // converts the unsigned integer hostlong from host byte order to network byte order 
    address.sin_port        = htons(port);         // converts the unsigned short integer hostshort from host byte order to network byte order

    // Check if IP-address is correct, if not Socket failed. Otherwise it returns the socket
    if(bind(sock, (struct sockaddr *) &address, sizeof(address))==-1)
    {
       fprintf(stderr, "2CreateSocket: bind failed\n");
       close(sock);
       return -1;
    }
    return sock;
}

Can anyone see any obvious errors here? Thanks

Answer 1

You don't really need these two lines:

char A = struct sockaddr_in address;
fprintf(stderr, A);

You can delete them, since they don't do anything useful, and they have a syntax error.

And to do some extra cleanup, the comment of the binding above those lines that can be deleted should actually go above the call to bind().