如何在 C/C++ 中的套接字编程中绑定地址？

Question

I want to bind address "95.96.10.1" with port number 8080. But when i tried below code it gave me error "address already in use".

#include <unistd.h> 
#include <stdio.h> 
#include <sys/socket.h> 
#include <stdlib.h> 
#include <netinet/in.h> 
#include <string.h> 
#define PORT 8080 
int main(int argc, char const *argv[]) 
{ 
int server_fd, new_socket, valread; 
struct sockaddr_in address; 
int opt = 1; 
int addrlen = sizeof(address); 
char buffer[1024] = {0}; 
char *hello = "Hello from server"; 

// Creating socket file descriptor 
if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) 
{ 
    perror("socket failed"); 
    exit(EXIT_FAILURE); 
} 


if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, 
                                              &opt, sizeof(opt))) 
{ 
    perror("setsockopt"); 
    exit(EXIT_FAILURE); 
} 
address.sin_family = AF_INET; 
address.sin_addr.s_addr = INADDR_ANY; 
address.sin_port = htons( PORT ); 

// Forcefully attaching socket to the port 8080 
if (bind(server_fd, (struct sockaddr *)&address,  
                             sizeof(address))<0) 
{ 
    perror("bind failed"); 
    exit(EXIT_FAILURE); 
} 

Please let me know how to bind address with port?

Answer 1

Currently, you're binding to INADDR_ANY which means to bind to all interfaces:

address.sin_addr.s_addr = INADDR_ANY; 

If you want to bind to a specific address, you need to set it. You can use the inet_addr function to convert an IPv4 string to an address value:

address.sin_addr.s_addr = inet_addr("95.96.10.1"); 

Also, socket options can't be OR'ed together. You can only operate on one at a time.

if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt))) 
{ 
    perror("setsockopt"); 
    exit(EXIT_FAILURE); 
} 
if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEPORT, &opt, sizeof(opt))) 
{ 
    perror("setsockopt"); 
    exit(EXIT_FAILURE); 
}