pikulet/findip.c

## findip.c
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

#define IP_ADDRESS_STRING_LENGTH 15

#define DELIMITERS "\r\n "
#define SERVER_HOSTNAME "nwtools.atwebpages.com"
#define SERVER_FILEPATH "/yourip.php"
#define SERVER_PORT 80

#define STATUS_OK_CODE "200"
#define CONTENT_LENGTH_HEADER "Content-Length"
#define HTML_BODY_TAG "<body>"

void getMyIP (char *result);

int main()
{
    char result[IP_ADDRESS_STRING_LENGTH];
    getMyIP(result);
    printf("My public IP address is %s\n", result);
    return 0;
}

void getMyIP (char *result)
{
    // Create socket
    int clientSocket = socket(AF_INET, SOCK_STREAM, 0);
    if (clientSocket == -1)
    {
        perror("Error creating socket");
        exit(-1);
    }

    // DNS resolution for hostname
    struct hostent *host;
    host = gethostbyname(SERVER_HOSTNAME);
    if (host == NULL)
    {
        perror("Error during DNS resolution");
        exit(-1);
    }

    // Connect to server
    struct sockaddr_in server_addr;
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(SERVER_PORT);
    server_addr.sin_addr = *((struct in_addr *)host->h_addr);
    bzero(&(server_addr.sin_zero),8);

    int connectionResult = connect(
            clientSocket,
            (struct sockaddr *)&server_addr,
            sizeof(struct sockaddr));
    if (connectionResult == -1)
    {
        perror("Error connecting to server");
        exit(1);
    }

    // Create HTTP request
    char httpRequest[1024];
    sprintf(httpRequest, "GET %s HTTP/1.1\r\nHost: %s\r\n\r\n",
            SERVER_FILEPATH, SERVER_HOSTNAME);
    // printf("Sending HTTP Request: \n%s", httpRequest);

    // Send HTTP Request
    int numBytesSent = send(clientSocket,
            httpRequest, strlen(httpRequest), 0);
    if (numBytesSent != strlen(httpRequest))
    {
        perror("Unable to send full message");
        exit(-1);
    }

    // Retrieve HTTP Response
    char httpReponse[1024];
    int numBytesReceived = recv(
            clientSocket,
            httpReponse,
            1024,
            0);
    httpReponse[numBytesReceived] = '\0';

    // Parse HTTP Response
    char *token = NULL;
    token = strtok(httpReponse, DELIMITERS);

    // Check status code
    token = strtok(NULL, DELIMITERS);

    int statusOK = strncmp(token, STATUS_OK_CODE, strlen(STATUS_OK_CODE));
    if (statusOK != 0)
    {
        printf("Did not receive status OK, please try again\n");
        exit(-1);
    }

    // Check content length
    int contentLengthFound = -1;
    while (token && contentLengthFound != 0)
    {
        token = strtok(NULL, DELIMITERS);
        contentLengthFound = strncmp(token, CONTENT_LENGTH_HEADER,
                strlen(CONTENT_LENGTH_HEADER));
    }

    token = strtok(NULL, DELIMITERS);
    int contentLength = atoi(token);
    if (contentLength <= 0)
    {
        printf("Did not receive any content, please try again\n");
        exit(-1);
    }

    // Parse for <body> opening tag
    int bodyTagFound = -1;
    while (token && bodyTagFound != 0)
    {
        token = strtok(NULL, DELIMITERS);
        bodyTagFound = strncmp(token, HTML_BODY_TAG, strlen(HTML_BODY_TAG));
    }

    token = strtok(NULL, DELIMITERS);
    for (int i = 0; i < IP_ADDRESS_STRING_LENGTH; i++)
    {
        result[i] = token[i + 3]; // offset for "IP:"
    }
}
	#include <sys/socket.h>
	#include <sys/types.h>
	#include <netinet/in.h>
	#include <arpa/inet.h>
	#include <netdb.h>
	#include <stdio.h>
	#include <string.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <errno.h>

	#define IP_ADDRESS_STRING_LENGTH 15

	#define DELIMITERS "\r\n "
	#define SERVER_HOSTNAME "nwtools.atwebpages.com"
	#define SERVER_FILEPATH "/yourip.php"
	#define SERVER_PORT 80

	#define STATUS_OK_CODE "200"
	#define CONTENT_LENGTH_HEADER "Content-Length"
	#define HTML_BODY_TAG "<body>"

	void getMyIP (char *result);

	int main()
	{
	char result[IP_ADDRESS_STRING_LENGTH];
	getMyIP(result);
	printf("My public IP address is %s\n", result);
	return 0;
	}

	void getMyIP (char *result)
	{
	// Create socket
	int clientSocket = socket(AF_INET, SOCK_STREAM, 0);
	if (clientSocket == -1)
	{
	perror("Error creating socket");
	exit(-1);
	}

	// DNS resolution for hostname
	struct hostent *host;
	host = gethostbyname(SERVER_HOSTNAME);
	if (host == NULL)
	{
	perror("Error during DNS resolution");
	exit(-1);
	}

	// Connect to server
	struct sockaddr_in server_addr;
	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(SERVER_PORT);
	server_addr.sin_addr = ((struct in_addr )host->h_addr);
	bzero(&(server_addr.sin_zero),8);

	int connectionResult = connect(
	clientSocket,
	(struct sockaddr *)&server_addr,
	sizeof(struct sockaddr));
	if (connectionResult == -1)
	{
	perror("Error connecting to server");
	exit(1);
	}

	// Create HTTP request
	char httpRequest[1024];
	sprintf(httpRequest, "GET %s HTTP/1.1\r\nHost: %s\r\n\r\n",
	SERVER_FILEPATH, SERVER_HOSTNAME);
	// printf("Sending HTTP Request: \n%s", httpRequest);

	// Send HTTP Request
	int numBytesSent = send(clientSocket,
	httpRequest, strlen(httpRequest), 0);
	if (numBytesSent != strlen(httpRequest))
	{
	perror("Unable to send full message");
	exit(-1);
	}

	// Retrieve HTTP Response
	char httpReponse[1024];
	int numBytesReceived = recv(
	clientSocket,
	httpReponse,
	1024,
	0);
	httpReponse[numBytesReceived] = '\0';

	// Parse HTTP Response
	char *token = NULL;
	token = strtok(httpReponse, DELIMITERS);

	// Check status code
	token = strtok(NULL, DELIMITERS);

	int statusOK = strncmp(token, STATUS_OK_CODE, strlen(STATUS_OK_CODE));
	if (statusOK != 0)
	{
	printf("Did not receive status OK, please try again\n");
	exit(-1);
	}

	// Check content length
	int contentLengthFound = -1;
	while (token && contentLengthFound != 0)
	{
	token = strtok(NULL, DELIMITERS);
	contentLengthFound = strncmp(token, CONTENT_LENGTH_HEADER,
	strlen(CONTENT_LENGTH_HEADER));
	}

	token = strtok(NULL, DELIMITERS);
	int contentLength = atoi(token);
	if (contentLength <= 0)
	{
	printf("Did not receive any content, please try again\n");
	exit(-1);
	}

	// Parse for <body> opening tag
	int bodyTagFound = -1;
	while (token && bodyTagFound != 0)
	{
	token = strtok(NULL, DELIMITERS);
	bodyTagFound = strncmp(token, HTML_BODY_TAG, strlen(HTML_BODY_TAG));
	}

	token = strtok(NULL, DELIMITERS);
	for (int i = 0; i < IP_ADDRESS_STRING_LENGTH; i++)
	{
	result[i] = token[i + 3]; // offset for "IP:"
	}
	}