How to run c++ CGI script on NGINX server

Question

I have written below lines in configuration file created in /etc/nginx/conf.d named as "helloworld.local.conf".

server{
     listen 80 default_server;
     server_name hello_world;
     location / {
          root /var/www/helloworld;
          fastcgi_pass 127.0.0.1:9000;
     } 
}

There is an index.html file in /var/www/helloworld which is displaying text "site comming soon".

My c++ code looks like below:

#include <iostream>
#include "fcgio.h"

using namespace std;

int main(void) {
    cout<<"Content-type:text/html\r\n\r\n";
    cout<<"<html>\n";
    cout<<"<head>\n";
    cout<<"<title>Hello World- First CGI Program</title>\n";
    cout<<"</head>\n";
    cout<<"<body>\n";
    cout<<"<h2> hello world</h2>\n";
    cout<<"</body>\n";
    cout<<"</html>\n";
    return 0;
}

I have the c++ binary code file is produced using the following command

g++ abc.cpp -lfcgi++ -lfcgi -o hello_world

which is needed to be deployed on the NGINX server. I searched and tried different ways to run this script on the stackoverflow but still missing something.

I also ran the below command to connect c++ binary code file to server

cgi-fcgi -start -connect 127.0.0.1:9000 ./hello_world

Now when i am visiting the address 127.0.0.1:9000 in the browser, not getting "hello world " text which is in the c++ code.

Output: I am suppose to get response as "hello world" from the the c++ binary code and that to be displayed on the html page.

What am i missing please help.

UPDATE: this is my config file now.

server{
    server_name hello;
    location / {
        fastcgi_index index.cgi;
        root /var/www/helloworld;
        fastcgi_pass 127.0.0.1:9000;
        fastcgi_param SCRIPT_FILENAME /scripts$fastcgi_name;
        include fastcgi_params;
    }
}

So what you want is to display the output of your program as html on a page served by your server? You are missing a lot of things. — KamilCuk, Mar 15 '19 at 22:28
Please have a look at output I am suppose to get. 3rd line from the last. — Atul Singh jadaun, Mar 16 '19 at 06:34
Please If i have missed something in above post let me know. — Atul Singh jadaun, Mar 16 '19 at 07:00

Amir · Accepted Answer · 2019-03-17T14:59:13.833

3

UPDATE

Take a look at this blog post. It explains how to setup C++/FCGI/nginx quite thoroughly.

ORIGINAL ANSWER

Your C++ code should be a listener (when it's running, it should listen to a port and return responses upon incoming requests). This part doesn't have anything to do with nginx. So first make sure that your code is working correctly; Run your code and try to access the specified port and see if you get the expected response.

Then you need to setup a proxy in your nginx configuration that basically redirects all of the traffic that you want to your C++ port (e.g 9000). For example you can set it up so that any url in the form of https://your_domain.com/api/* redirects to your C++.

This is pretty easy in nginx:

location /api/ {
    proxy_pass  http://127.0.0.1:9000/;
}

But first test your C++ alone, and make sure it works fine

Also you'd better use something like runit, systemd, or similar tools to keep your C++ listener running (restart it if it crashes).

edited Mar 17 '19 at 14:59

answered Mar 15 '19 at 21:45

Amir

1,885
3
19
36

1

I think you might have misunderstood the OP; he's not trying to build a server in C++, he's just trying to build a CGI module in C++. – Jose Fernando Lopez Fernandez Mar 16 '19 at 07:06
You are right #Jose Fernando Lopez Fernandez I am trying to build a fast CGI script to print "hello world" on the html page on visiting any specific page url. – Atul Singh jadaun Mar 16 '19 at 07:21
1

Thank you @Amir for your time and help and efforts. I have gone through that post link but it was not helping. – Atul Singh jadaun Mar 16 '19 at 07:30
The problem is with the script that i have written. Thanks. – Atul Singh jadaun Mar 19 '19 at 19:22

score 0 · Answer 2 · answered Mar 16 '19 at 07:21

0

Unless you're calling your CGI script (or executable in this case) through a form, I think it would be simpler with no loss of generality to just make that your index. As you currently have it, the fact that you're not seeing anything isn't surprising. Remember that the CGI module isn't appending anything to the first html file. You have to declare the content type on the first line because it is the html file that will be displayed.

I would change the compilation to this though:

g++ abc.cpp -lfcgi++ -lfcgi -o index.cgi

Now, in your configuration file, make sure you have the following. I normally use Apache, but if I'm not mistaken, your folder configuration should look like this and you should be good to go.

location / {
    root          /var/www/helloworld;
    fastcgi_pass  127.0.0.1:9000;
    fastcgi_index index.cgi
    fastcgi_param SCRIPT_FILENAME $fastcgi_script_name
    include       fastcgi_params
}

From the documentation, the fastcgi_param argument usually looks like this:

fastcgi_param SCRIPT_FILENAME /scripts$fastcgi_script_name

Since your I presupposed that your executable would be called index.cgi and would be in the current directory, I left out the scripts folder from the example, but keep in mind this example is extremely contrived, and valuable really only for getting the most minimal CGI system going.

answered Mar 16 '19 at 07:21

Jose Fernando Lopez Fernandez

1,139
9
18

Thanks for your help and time. Now, I am trying your suggestions. I will comment here with the updates. – Atul Singh jadaun Mar 16 '19 at 07:26
If i put my index.cgi script in the /var/www/helloworld directory then what should be the $fast_script_name? – Atul Singh jadaun Mar 16 '19 at 07:50
That's actually just a variable declaration; that line is telling the server how to pass the SCRIPT_FILENAME parameter. You should leave that as is. – Jose Fernando Lopez Fernandez Mar 16 '19 at 08:44
I performed both the major steps that you mentioned above about location directive and command for creating index.cgi and also deleted index.html from the /etc/www/helloworld directory and placed index.cgi there still not getting any respose. – Atul Singh jadaun Mar 16 '19 at 08:57
Is there is anything else you think i missed? – Atul Singh jadaun Mar 16 '19 at 08:58
Can you post your entire config file? I'll take a look – Jose Fernando Lopez Fernandez Mar 16 '19 at 09:13

How to run c++ CGI script on NGINX server

2 Answers2