What is wrong with this "simple-http-server" program (c code)

Question

The follow is a simple piece of code I wrote to demonstrate how HTTP server works. I compiled it run it under cygwin, but I cannot use web browser to connect to this simple http server. And after running the simple http server, I can still run apache at port 80, and if apache is not running, "netstat -an" show that port 80 is not occupied.

I wrote another simple program which sends a simple "hello" string to the simple http server, and then got the responses.

What's wrong with this program? why I cannot connect it using web browser, but I can connect it with another simple program?
When is a port been occupied? After "bind" or "listen"?
If one application is using a port of a particular network interface (say 192.168.2.1:80, suppose more than one network interfaces exist), can another application use the same port at another interface (say 192.168.55.1:80)?
when running httpd, there are more than one httpd processes in the processes list, only one is using 0.0.0.0:80, if using cygwin apache, other httpd is using other UDP port? Why?


#include "stdio.h"
#include "stdlib.h"
#include "string.h"

#include "sys/types.h"
#include "sys/socket.h"
#include "netinet/in.h"
#include "netdb.h"
#include "unistd.h"
#include "fcntl.h"


#define PORT 80

char HttpHeader[1000];

char HeaderTemplate[] =
    "HTTP/1.0 200 OK\r\n"
    "Server: PRIMITIVE Server\r\n"
    "Date: %s\r\n"
    "Content-Type: text/html\r\n"
    "Accept-Ranges: bytes\r\n"
    "Content-Length: %d\r\n\r\n";

char PageContent[] = "Hello World!";


char GMTNow[] = "11/15/14 00:59:00 GMT";
char ClntRequest[1000];   

struct sockaddr_in SocketAddress;
int ClntDescriptor;   /* socket descriptor to  client */
int SrvrDescriptor;   /* socket descriptor for server */

int main(int argc, char* argv[])
{
    sprintf(HttpHeader, HeaderTemplate, GMTNow, strlen(PageContent));

    SrvrDescriptor = socket(AF_INET, SOCK_STREAM, 0);
    SocketAddress.sin_family      =  AF_INET;
    SocketAddress.sin_port        =  PORT;
    SocketAddress.sin_addr.s_addr =  INADDR_ANY;
    bind(SrvrDescriptor, (struct sockaddr*)&SocketAddress, sizeof(SocketAddress));

    listen(SrvrDescriptor, 5);
    ClntDescriptor = accept(SrvrDescriptor, 0, 0);

    while (1)
    {
        recv(ClntDescriptor, ClntRequest, sizeof(ClntRequest), 0);
        printf("%s\n", ClntRequest);

        write(ClntDescriptor, HttpHeader, strlen(HttpHeader));
        write(ClntDescriptor, PageContent, strlen(PageContent));

        printf("%s", HttpHeader);
        printf("%s", PageContent);
    }

    close(SrvrDescriptor);

    return EXIT_SUCCESS;
}

2. you'd receive an error return from the bind call if the port is already in use. — 9dan
– 9dan, Commented Jan 1, 2011 at 4:12

Steve-o · Accepted Answer · 2011-01-01 03:58:22Z

1

Port is in the incorrect byte order,

SocketAddress.sin_port        =  htons (PORT);

answered Jan 1, 2011 at 3:58

Steve-o

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Himanshu · Accepted Answer · 2011-01-01 04:10:05Z

0

What's wrong with this program? why I cannot connect it using web browser, but I can connect it with another simple program?

Most probably your port needs to be in network byte order. Use htons(PORT).
When is a port been occupied? After "bind" or "listen"? After bind.
If one application is using a port of a particular network interface (say 192.168.2.1:80, suppose more than one network interfaces exist), can another application use the same port at another interface (say 192.168.55.1:80)? Yes.

answered Jan 1, 2011 at 4:10

Himanshu

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