Function to make a POST request to a server using windows sockets in C.

win-http-client.h

/**
	This function makes a connection to the server,
	sends the data and retreive the response.
	
	Don't forget to include:	
	#include <winsock2.h>
	
	And to add this to your code:
	#pragma comment(lib,"ws2_32.lib") //Winsock Library
**/
unsigned char sendToServer(const char *address, int port, char *uri, char *data){
        
	WSADATA wsa;
	
	if (WSAStartup(MAKEWORD(2,2),&wsa) != 0){
		fprintf(stderr, "ERROR: Failed to Initialize Socket %d \n", WSAGetLastError());
		return 0;
	}
	
    SOCKET s;
    struct sockaddr_in server;    

    //Create a TCP Socket
    /*
        AF_INET     -   This is IPv4
        SOCK_STREAM -   This means connection oriented TCP (SOCK_DGRAM - UDP)
        0           -   Use IPPROTO_TCP
    */
    if((s = socket(AF_INET , SOCK_STREAM , 0 )) == INVALID_SOCKET){
        fprintf(stderr, "ERROR: Could not create socket %d \n", WSAGetLastError());
        return 0;
    }

    server.sin_addr.s_addr = inet_addr(address);     //Set server address
    server.sin_family = AF_INET;                     //Set IPv4
    server.sin_port = htons(port);                   //Set server port

    //Connect to remote server
	printf("LOG: Connecting to server... \n");

    if (connect(s, (struct sockaddr *)&server, sizeof(server)) != 0){
        fprintf(stderr, "ERROR: Connecting to server \n");
        closesocket(s);
        return 0;
    }

    //Create HTTP Message
    char *message;
        if((message = (char *) calloc(2*strlen(data), sizeof(char))) == NULL)
            perror("ERROR");
    char *content;
        if((content = (char *) calloc(strlen(data)+1, sizeof(char))) == NULL)
            perror("ERROR");
    char host[64];
    host[0] = '\0';

    sprintf(content, data);
    sprintf(host, address, ":", port);

    sprintf(message, "\
POST %s HTTP/1.1\r\n\
Host: %s\r\n\
Connection: keep-alive\r\n\
Content-Type: application/json; charset=utf-8;\r\n\
Content-Length: %d\r\n\
Pragma: no-cache\r\n\
Cache-Control: no-cache\r\n\r\n\
%s\r\n", uri, host, strlen(content), content);


    //SEND DATA TO SERVER
    if( send(s, message, strlen(message), 0) < 0){
        fprintf(stderr, "ERROR: Failed sending message to server \n");  
        free(content);
        free(message);
        closesocket(s);
        return 0;
    }
	
    printf("\tLOG:\t...Data sent to server!\n");



    //GET DATA FROM SERVER
    char server_reply[65536];
    int recv_size;

    if((recv_size = recv(s , server_reply , 65536 , 0)) == SOCKET_ERROR){
        fprintf(stderr, "ERROR: Failed receiving message from the server \n");
        free(content);
        free(message);
        closesocket(s);
        return 0;
    }

    //Add a NULL terminating character to make it a proper string before printing
    server_reply[recv_size] = '\0';
    
    printf("LOG: Server response: \n %s \n", server_reply);

    free(content);
    free(message);
    closesocket(s);
	
	WSACleanup();
	
    return 1;
}