HTTP Request in C using low level write to socket functionality

socket.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

#include <netinet/tcp.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>

int socket_connect(char *host, in_port_t port){
	struct hostent *hp;
	struct sockaddr_in addr;
	int on = 1, sock;     

	if((hp = gethostbyname(host)) == NULL){
		herror("gethostbyname");
		exit(1);
	}
	bcopy(hp->h_addr, &addr.sin_addr, hp->h_length);
	addr.sin_port = htons(port);
	addr.sin_family = AF_INET;
	sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
	setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (const char *)&on, sizeof(int));

	if(sock == -1){
		perror("setsockopt");
		exit(1);
	}
	
	if(connect(sock, (struct sockaddr *)&addr, sizeof(struct sockaddr_in)) == -1){
		perror("connect");
		exit(1);

	}
	return sock;
}
 
#define BUFFER_SIZE 1024

int main(int argc, char *argv[]){
	int fd;
	char buffer[BUFFER_SIZE];

	if(argc < 3){
		fprintf(stderr, "Usage: %s <hostname> <port>\n", argv[0]);
		exit(1); 
	}
       
	fd = socket_connect(argv[1], atoi(argv[2])); 
	write(fd, "GET /\r\n", strlen("GET /\r\n")); // write(fd, char[]*, len);  
	bzero(buffer, BUFFER_SIZE);
	
	while(read(fd, buffer, BUFFER_SIZE - 1) != 0){
		fprintf(stderr, "%s", buffer);
		bzero(buffer, BUFFER_SIZE);
	}

	shutdown(fd, SHUT_RDWR); 
	close(fd); 

	return 0;
}

I am trying to send a Telegram message using HTTP GET. However, I don't know how to pass the required parameters. I have try this:
"GET / HTTP/1.1\r\nHost: https://api.telegram.org/botmybottokenhere/sendMessage?chat_id=mychatidhere&text=mymessagehere\r\nConnection: close\r\n\r\n"
but does not work. I get a 400 bad request error. But if I copy that url and paste it in Chrome the message is sent, so the url is correct. It also works in Python3.7.

You're getting the 400 error because you are sending an HTTP request to an HTTPS-encrypted endpoint. For what it's worth, I stumbled upon your comment because I am running into this exact same issue and I am trying to figure out how to send an HTTPS-based request using the low-level socket_*() functions. If I figure this out then I'll try to pop back in here and see if I can share my knowledge.

The response I receive in my own attempts are as follows:

400 The plain HTTP request was sent to HTTPS port
400 Bad Request
The plain HTTP request was sent to HTTPS port

I think you need to add something like this to add TLS :

int client_fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TLS_1_2);
enum {
NONE = 0,
OPTIONAL = 1,
REQUIRED = 2,
};

int verify = OPTIONAL;

err = setsockopt(client_fd, SOL_TLS, TLS_PEER_VERIFY, &verify, sizeof(verify));

Error - IPPROTO_TLS_1_2 is not defined..........

@Andermutu it has been a while , but in case you're still interested :)

This is not valid HTTP:

"GET / HTTP/1.1\r\nHost: [https://api.telegram.org/botmybottokenhere/sendMessage?chat_id=mychatidhere&text=mymessagehere\r\nConnection](https://api.telegram.org/botmybottokenhere/sendMessage?chat_id=mychatidhere&text=mymessagehere%5Cr%5CnConnection): close\r\n\r\n"

The host header should contain only the host. You've given it a full URL!

And your request path is just / so it would never work.

Also, you're trying to send a https request which means the socket needs to be encrypted. And notice that the protocol doesn't go in the HTTP request itself as that refers to the transport being used.

So, your request should look like this (\r\n replaced with simple new-lines for readability, you still need them in a real request):

GET /botmybottokenhere/sendMessage?chat_id=mychatidhere&text=mymessagehere HTTP/1.1
Host: api.telegram.org
Connection: close

@dimuthnc

localhost:8080/services

write(fd, "GET /services HTTP/1.1\r\n\r\n", strlen("GET /services HTTP/1.1\r\n\r\n"));

Run command:

gcc socket.c -o socket
./socket localhost 8080

You may want to use bcopy instead of copy at line 22