binding errors: "cannot assign requested address" and "permission denied" [duplicate] - c++

Question

Following code is TCP server program just send back “HELLO!!” to client.
When I run server with port 80, bind() is returned Permission denied.
Port 12345 is OK.
How can I use port 80 for this server program?
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
int
main(){
int sock0;
struct sockaddr_in addr;
struct sockaddr_in client;
int len;
int sock;
char *message;
message = "HELLO !!";
sock0 = socket(AF_INET,SOCK_STREAM,0);
addr.sin_family = AF_INET;
addr.sin_port = htons(80);
inet_pton(AF_INET,"127.0.0.1",&addr,sizeof(addr));
bind(sock0,(struct sockaddr *)&addr,sizeof(addr));
perror("bind");
len = sizeof(client);
sock = accept(sock0,(struct sockaddr *)&client,&len);
perror("accept");
write(sock,message,sizeof(message));
perror("write");
close(sock);
return 0;
}

Answer 1

Ports below 1024 are considered "privileged" and can only be bound to with an equally privileged user (read: root).
Anything above and including 1024 is "free to use" by anyone.
OT: you may know this already, but the port in your example is that for HTTP web servers. Anything listening to this port should speak HTTP, too. A simple "hello world" does not suffice. ;-)

Answer 2

Only the root user is allowed to bind to ports <= 1024. Every ports > 1024 can be bound to by normal users.
Try executing your program as root or with sudo.

Answer 3

you have to run your application with super user account (root)
Run your application with sudo command