Sending a POST request using a Socket, but using much of memory power

Question

This long code is sending a POST request using a Socket, the whole code works without any complain, but what i'm facing right now is, that it eating a lot of cpu power, uses too much memory (RAM)

I can see that, because my laptop is getting hot very fast and by looking checking at my mac.

i have tried to find the bug or where , that very large memory Issue is, but couldn't. I have spent over a month trying to fix it by my own, but don't know what i'm doing to be honest.

i was so desperate, that i putted all kind of freeing metod.. even that it wrong.. just to see if that made a change, but nothing did..

So now i don't know what wrong or how to fix this, please help me out…

Going update the code with select, moment... trying to clean it up first

Answer 1

First thing: do NOT mix malloc() and delete[]. They might or might not refer to the same memory allocator. So use the malloc()/free() or new char[]/delete[] pairs.

The problems is here (in Database() function): you've got a terrible memleak. Do not allocate memory like this for result passing. Better use buffers. You program is multithreaded so use the buffers on the stack. Do NOT call delete[] on anything that is not allocated by you (var declaration like "char Buf[100];" is not an allocation).

New version (I omitted main() and strip() functions. Also the includes):

#define MAX_ECHO_SIZE (1024)
#define MAX_RESPONSE_SIZE (1024)

void process_http(int sockfd, const char *host, const char *page, const char *poststr, char* OutResponse)
 {
    char* ptr;
    char sendline[MAXLINE + 1], recvline[MAXLINE + 1];
    ssize_t n;

    snprintf(sendline, MAXSUB, 
         "POST %s HTTP/1.0\r\n"  // POST or GET, both tested and works. Both HTTP 1.0 HTTP 1.1 works, but sometimes 
         "Host: %s\r\n"     //oth HTTP 1.0 HTTP 1.1 works, but sometimes HTTP 1.0 works better in localhost type
         "Content-type: application/x-www-form-urlencoded\r\n"
         "Content-length: %d\r\n\r\n"
         "%s\r\n", page, host, (unsigned int)strlen(poststr), poststr);

    if (write(sockfd, sendline, strlen(sendline))>= 0) 
    {
        while ((n = read(sockfd, recvline, MAXLINE)) > 0) 
        {
            recvline[n] = '\0';

            if(fputs(recvline,stdout) ==EOF) { cout << ("fputs erros"); }
            ptr = strstr(recvline, "\r\n\r\n");
            strip(ptr, "\r\n\r\n");

            // check len for OutResponse here ?
            snprintf(OutResponse, 6000,"%s", ptr);
        }
    }
}

int Database( const char * hname,  const char * page,  const char * var, const char * poststr,  int  port, char* EchoResponse, int MaxEchoLen){

    char url[MAXLINE];
    char response[MAX_RESPONSE_SIZE];

    snprintf(url, MAXLINE, "%s=%s", var, poststr);

    short int sockfd ;
    struct sockaddr_in servaddr;
    struct hostent *hptr;
    char str[MAXLINE];
    char** pptr;

    hptr = gethostbyname(hname);

    sockfd = socket(AF_INET, SOCK_STREAM, 0);

    if (!hptr) {
        cout << ("host not found\n");
        return -1; // "host not found";
    }

    if (hptr->h_addrtype == AF_INET && (pptr = hptr->h_addr_list) != NULL) {
        inet_ntop(hptr->h_addrtype, *pptr, str, sizeof(str)); 
    }
    if (sockfd  >= 0  ) {
        bzero(&servaddr, sizeof(servaddr));
        servaddr.sin_family = AF_INET;
        servaddr.sin_port = htons(port);
        inet_pton(AF_INET, str, &servaddr.sin_addr);

        if (connect(sockfd, (SA *) & servaddr, sizeof(servaddr)) < 0) {
            return -2; // "Server down, connect error";
        }
        else {
            process_http(sockfd, hname, page, url, &response[0], MAX_RESPONSE_SIZE);

            int len = strlen(response)+1;
            if(len >= MaxEchoLen) { return -3; /* buffer too small*/ }

            // Copy the contents with
            strcpy(EchoResponse, response);

            /// You must not free all of char[] allocated on stack
            close(sockfd);

            return 0; // OK
        }
    }
}

void *multithreading1( void *ptr ) {
    char LocalEchoResponse[MAX_ECHO_SIZE];

    while (1) {
            int RetCode = Database("2.107.xx.xxx", "/ajax.php", "submit", "HEllo WORLD", 80, &LocalEchoResponse[0], MAX_ECHO_SIZE);
            /// check the error
    }   
}

Answer 2

You have a pretty big memory leak in strip_copy. Whatever you put after the return will never get executed. Im surprised the compiler didnt complain about this. Same problem in the process_http() function.

Fix it like this:

static void strip_copy(char const *s, char *buf, const char * SPACE)
{
    if (buf)
    {
        char *p = buf;
        char const *q;
        int n;
        for (q = s; *q; q += n + strspn(q+n, SPACE))
        {
            n = strcspn(q, SPACE);
            strncpy(p, q, n);
            p += n;
        }
        *p++ = '\0';
        buf = (char*)realloc(buf, p - buf);
    }
}

// Then call it like this
char *buf = new[1 + strlen(s)];
strip_copy(s, buf, ' ');
// use buf
delete [] buf;

And in process_http()

const char*  process_http(int sockfd, const char *host, const char *page, const char *poststr)
{
    ....
    // delete here only what you dynamically 
    // allocated with new() BEFORE the return
    return response; // n
}

And DONT mix malloc() with delete():

• malloc() goes with free()
• new() goes with delete()

This isnt related to the memory used, but instead of calling read()/write() directly, you should use select() to know when its ready to be read or written. Here's a related question: https://stackoverflow.com/a/10800029/1158895