Method of using raw sockets - c

Question

I am using raw sockets for the first time, so excuse me if my question exhibits serious lack of knowledge in this field.
My goal is to make a client-server program using raw sockets where client can send a string to server and server can send a reply. My codes are as follows:
/* server.c */
#include "../cn.h"
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
int main(int argc, char const *argv[]) {
int sfd = socket(AF_INET, SOCK_RAW, 253);
if (sfd < 0) {
perror("Could not create socket");
exit(0);
}
struct sockaddr_in addr;
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
if (bind(sfd, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
perror("Could not bind");
}
int nsfd = accept(sfd, NULL, NULL);
if (nsfd < 0) {
perror("Could not accept");
exit(0);
}
char buffer[20];
int sz;
while (1) {
if ((sz = read(nsfd, buffer, 20)) < 0) {
perror("Could not read");
} else {
buffer[sz] = '\0';
strcat(buffer, " form server");
if (write(nsfd, buffer, strlen(buffer)) < 0) {
perror("Could not send");
}
}
}
return 0;
}
Client code:
#include "../cn.h"
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
int main(int argc, char const *argv[]) {
int sfd = socket(AF_INET, SOCK_RAW, 253);
if (sfd < 0) {
perror("Could not create socket");
exit(0);
}
struct sockaddr_in addr;
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
if (connect(sfd, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
perror("Could not connect");
exit(0);
}
char buffer[20];
int sz;
while (1) {
scanf("%[^\n]s", buffer);
while (getchar() != '\n')
;
if (write(sfd, buffer, strlen(buffer)) < 0) {
perror("Could not write");
} else
if ((sz = read(sfd,buffer, 20)) < 0) {
perror("Could not read");
} else {
buffer[sz] = '\0';
printf("Reading: %s\n", buffer);
}
}
return 0;
}
Whenever I am trying to run the programs , it is showing error at the very time of socket creation itself:
Could not create socket: Operation not permitted
My questions are:
What am I missing in this case? Why does is this operation not permitted?
Though it is a broad question but, how to use raw sockets with custom protocol ID?
Is there any good material available for use of raw sockets with custom protocol?