HTTP GET request

This is a discussion on HTTP GET request within the C Programming forums, part of the General Programming Boards category; From my knowledge of HTTP sending a get request via HTTP with c (I'm only worried about get) should just ...

  1. #1
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    HTTP GET request

    From my knowledge of HTTP sending a get request via HTTP with c (I'm only worried about get) should just be sending a packet containing something like GET <filename> HTTP/1.0 ... I've been trying to do it with something like this:

    Code:
    	request = malloc( ((tok - &(*argv[1])) - sizeof(argv[1])) + sizeof(char) * 17 + 1 + 4 );
    	sprintf(request, "%s %s %s", "GET", &(*argv[1]) + (tok - &(*argv[1])), "HTTP/1.0");
    	printf("%s\n", request);
    	serverSocket = socket(AF_INET, SOCK_STREAM, 0);
    	if (serverSocket == -1)
    		error("socket()");
    	if (connect(serverSocket, (struct sockaddr *)&serverAddr, sizeof(serverAddr)) != 0)
    		error("connect()");
    	if (send(serverSocket, &request, sizeof(request), 0) < 0)
    		error("send()");
    do I have to hton this data? I'm not getting a response from the server.

    TIA

  2. #2
    Or working on it anyways mramazing's Avatar
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    you might have to end it with \r\n\r\n that is how the server knows the request is done. If I remember correctly the request should look something like this in c...

    Code:
         char request[] = "GET /index.html HTTP/1.1\r\n",
                                    "host: somewebsite.com\r\n",
                                    "\r\n";
    -- Will you show me how to c++?

  3. #3
    CSharpener vart's Avatar
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    Code:
    request = malloc( ((tok - &(*argv[1])) - sizeof(argv[1])) + sizeof(char) * 17 + 1 + 4 );
    what length are you trying to allocate here?
    Code:
    	sprintf(request, "%s %s %s", "GET", &(*argv[1]) + (tok - &(*argv[1])), "HTTP/1.0");
    why not
    Code:
    	sprintf(request, "GET %s HTTP/1.0", tok);
    Code:
    	if (send(serverSocket, &request, sizeof(request), 0) < 0)
    		error("send()");
    sizeof (request) is 4 bytes
    so you just sent the pointer to request - instead of the request itself...

    use Wireshark to check what is being sent to network
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  4. #4
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    MrAmazing and Vart - Thanks for the responses.

    I caught the sprintf while debugging:

    Code:
    sprintf(request, "GET %s HTTP/1.0\r\nHOST:%s \r\n", &(*argv[1]) + (tok - &(*argv[1])), host);
    That terrible malloc is because I need the length of the requested file, minus the domain (example.com).

    size problems fixed:

    Code:
    i = send(serverSocket, &request, strlen(request) * sizeof(char), 0);
    if (strlen(request) != i)
    {
    	printf("%d , %d\nMismatch!\n", i, strlen(request));
    }
    printf("request sent!\n%d\n", i);
    printf("waiting for response...\n");
    printf("%d", recv(serverSocket, &buffer, sizeof(buffer), 0));
    now I'm hanging on the receive (why it's in the printf).

    I can see a packet going out with a payload of 44bytes (in the case of the data I was using my request was 44 bytes). The rest are just SYN ACK (no response from server). the payload the of packet is:

    Code:
    00000   00 40 10 20 00 01 00 25  56 11 bf 49 08 00 45 00    .@. ...%V..I..E.
    00010   00 60 b1 9f 40 00 40 06  70 dd c0 a8 01 02 4a 36    .`..@.@.p.....J6
    00020   0c 3b d6 cd 00 50 15 a0  25 7f d4 28 0b ce 80 18    .;...P..%..(....
    00030   ff ff 0b fb 00 00 01 01  08 0a 29 f0 3c 27 94 35    ..........).<'.5
    00040   d7 79 47 45 54 20 2f 69  6e 64 65 78 2e 70 68 70    .yGET /index.php
    00050   20 48 54 54 50 2f 31 2e  30 0d 0a 48 4f 53 54 3a     HTTP/1.0..HOST:
    00060   61 63 65 6e 73 75 6d 2e  63 6f 6d 20 0d 0a          acensum.com ..
    compete (albeit rather messy right now) code:

    Code:
    #include <stdio.h>
    #include <string.h>
    #include <sys/socket.h>
    #include <sys/types.h>
    #include <stdlib.h>
    #include <netinet/in.h>
    #include <arpa/inet.h>
    #include <netdb.h>
    #include <stdbool.h>
    #include <unistd.h>
    
    #define BUFFSIZE 512
    
    void error(char *msg);
    
    int serverSocket;
    int i = 0;
    size_t bWritten, bTotal;
    struct sockaddr_in serverAddr;
    struct hostent *hostptr;
    char *ip = "74.54.12.59";
    char *tok, *host, *request, *buffer[BUFFSIZE];
    
    
    int main (int argc, const char * argv[]) {
    	printf("%s rev.0\n", argv[0]);
    	if (argc < 2)
    	{
    		printf("Usage: %s [address]\n", argv[0]);
    		exit(-1);
    	}
    	memset(&serverAddr, 0, sizeof(serverAddr));
    	serverAddr.sin_family = AF_INET;
    	serverAddr.sin_port = htons(80);
    	serverAddr.sin_addr.s_addr = inet_addr(ip);
    	tok = strpbrk(argv[1], "/");
    	host = malloc(sizeof(char) * (tok - &(*argv[1]) + 1));
    	strncpy(host, argv[1], tok - &(*argv[1]) );
    	//disabled because xcode has a problem with gethostbyname()
    	//char *test = "acenusm.com";
    	//hostptr = gethostbyname(test);
    	//printf("Resolved: %s\n", host);
    	//printf("%s \n", hostptr->h_addr_list[0]);
    	//these are really nasty but they work.
    	printf("Requesting: %s\n", argv[1] + (tok - argv[1]));
    	request = malloc( (tok - argv[1]) - strlen(argv[1]) + sizeof(char) * 26 + strlen(host) + 1 );
    	sprintf(request, "GET %s HTTP/1.0\r\nHOST:%s \r\n", argv[1] + (tok - argv[1]), host);
    	//free and Null pointer
    	if(host)
    	{
    		free(host);
    		host = NULL;
    	}
    	serverSocket = socket(AF_INET, SOCK_STREAM, 0);
    	if (serverSocket < 0)
    		error("socket()");
    	if (connect(serverSocket, (struct sockaddr *)&serverAddr, sizeof(serverAddr)) < 0)
    		error("connect()");
    	for (bTotal = 0; bTotal < strlen(request); bTotal += bWritten)
    	{
    		bWritten = write(serverSocket, &request[bTotal], strlen(request) - bTotal);
    		if (bWritten == 0)
    			break;
    	}
    	//i = send(serverSocket, &request, (strlen(request) + 1), 0);
    	//if (strlen(request) + 1 != i)
    	//	error("send()");
    	printf("waiting for response...\n");
    	//assuming recv return 0 when socket is closed)
    	FILE *fp;
    	fp = fopen("default.txt", "a");
    	for(int j; j < BUFFSIZE; j++)
    	{
    		i = recv(serverSocket, &buffer+j, 4, 0);
    		printf("%s\n", buffer);
    	}
    	free(request);
    	request = NULL;
    	
    }
    
    void error(char *msg)
    {
    	printf("Error: %s\n", msg);
    	perror("");
    	exit(0);
    }
    Last edited by aosmith; 03-21-2010 at 03:10 AM. Reason: cleaned up code

  5. #5
    a_capitalist_story
    Join Date
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    You need TWO \r\n pairs at the end of the request:
    Code:
    sprintf(request, "GET %s HTTP/1.0\r\nHOST:%s \r\n\r\n", argv[1] + (tok - argv[1]), host);
    It's hanging because the server is waiting for the second one.

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