Integrating IBM i CGI programs into Linux Web Server

We have been working with a number of clients now who have CGI programs (mainly RPG) that have been used as part of web sites which were hosted on the IBM Apache Server. These programs build the page content using a write to StdOut process. They have now started the migration to PHP based web sites and need to keep the CGI capability until they can re-write the existing CGI application to PHP.

The clients are currently running the iAMP server (they could use the ZendServer as well) for their PHP content and will need to access the CGI programs from that server. We wanted to test the process would run regardless of the Apache server used (IBM i, Windows,Linux etc) so we decided to set up the test using our Linux Apache server. The original PHP Server on the IBM i used a process that involved the passing of requests to another server (ProxyPass) which is what we will use to allow the Linux Server to get the CGI content back to the originating request. If you want to know more about the Proxy Process you can find it here.

First of we set up the IBM Apache Server to run the CGI program which we need. The program is from the IBM knowledge center called SampleC which I hacked to just use the POST method (code to follow) which I complied into a library called WEBPGM. Here is the content of the httpd.conf for the apachedft server.


# General setup directives
Listen 192.168.200.61:8081
HotBackup Off
TimeOut 30000
KeepAlive Off
DocumentRoot /www/apachedft/htdocs
AddLanguage en .en
DefaultNetCCSID 819
Options +ExecCGI -Includes
CGIJobCCSID 37
CGIConvMode %%EBCDIC/MIXED%%
ScriptAliasMatch ^/cgi-bin/(.*).exe /QSYS.LIB/WEBPGM.LIB/$1.PGM

The Listen line states that the server is going to listen on port 8081. Options allows the execution of CGI progrmas (+ExecCGI). I have set the CGI CCSID and conversion mode and then set up the re-write of any request that has a url with ‘/cgi-bin/’ and has a extension of .exe to the library format required to call the CGI program.

The program is very simple, I used the C version of the program samples IBM provides and hacked the content down to the minimum I needed. I could have altered it even further to remove the write_data() function but it wasn’t important. Here is the code for the program which was compiled into the WEBPGM lib.


#include <stdio.h> /* C-stdio library. */
#include <string.h> /* string functions. */
#include <stdlib.h> /* stdlib functions. */
#include <errno.h> /* errno values. */
#define LINELEN 80 /* Max length of line. */

void writeData(char* ptrToData, int dataLen) {
div_t insertBreak;
int i;

for(i=1; i<= dataLen; i++) {
putchar(*ptrToData);
ptrToData++;
insertBreak = div(i, LINELEN);
if( insertBreak.rem == 0 )
printf("<br>");
}
return;
}

void main( int argc, char **argv) {
char *stdInData; /* Input buffer. */
char *queryString; /* Query String env variable */
char *requestMethod; /* Request method env variable */
char *serverSoftware; /* Server Software env variable*/
char *contentLenString; /* Character content length. */
int contentLength; /* int content length */
int bytesRead; /* number of bytes read. */
int queryStringLen; /* Length of QUERY_STRING */

printf("Content-type: text/htmln");
printf("n");
printf("<html>n");
printf("<head>n");
printf("<title>n");
printf("Sample AS/400 HTTP Server CGI programn");
printf("</title>n");
printf("</head>n");
printf("<body>n");
printf("<h1>Sample AS/400 ILE/C program.</h1>n");
printf("<br>This is sample output writing in AS/400 ILE/Cn");
printf("<br>as a sample of CGI programming. This program readsn");
printf("<br>the input data from Query_String environmentn");
printf("<br>variable when the Request_Method is GET and readsn");
printf("<br>standard input when the Request_Method is POST.n");
requestMethod = getenv("REQUEST_METHOD");
if ( requestMethod )
printf("<h4>REQUEST_METHOD:</h4>%sn", requestMethod);
else
printf("Error extracting environment variable REQUEST_METHOD.n");
contentLenString = getenv("CONTENT_LENGTH");
contentLength = atoi(contentLenString);
printf("<h4>CONTENT_LENGTH:</h4>%i<br><br>n",contentLength);
if ( contentLength ) {
stdInData = malloc(contentLength);
if ( stdInData )
memset(stdInData, 0x00, contentLength);
else
printf("ERROR: Unable to allocate memoryn");
printf("<h4>Server standard input:</h4>n");
bytesRead = fread((char*)stdInData, 1, contentLength, stdin);
if ( bytesRead == contentLength )
writeData(stdInData, bytesRead);
else
printf("<br>Error reading standard inputn");
free(stdInData);
}
else
printf("<br><br><b>There is no standard input data.</b>");
printf("<br><p>n");
serverSoftware = getenv("SERVER_SOFTWARE");
if ( serverSoftware )
printf("<h4>SERVER_SOFTWARE:</h4>%sn", serverSoftware);
else
printf("<h4>Server Software is NULL</h4>");
printf("</p>n");
printf("</body>n");
printf("</html>n");
return;
}

Sorry about the formatting!

That is all we had to do on the IBM i server, we restarted the default apache instance and set to work on creating the content required for the Linux Server.
The Linux Server we use is running Proxmox, this allows us to build lots of OS instances (Windows,Linux etc) for testing. The Virtual Server is running a Debian Linux build with a standard Apache/PHP install. The Apache servers are also running Virtual hosts (we have 3 Virtual Linux servers running Apache), this allows us to run many websites from a single server/IP address. We created a new server called phptest (www.phptest.shield.local) running on port 80 some time ago for testing our PHP scripts so we decided to use this server for the CGI test. As the Server was already running PHP scripts all we had to do was change the configuration slightly to allow us to pass the CGI requests back to the IBM i Apache server.

The sample code provided by IBM which will run on the Linux Server is listed below.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
</head>

<body>
<form method="POST" action="/cgi-bin/samplec.exe">
<input name="YourInput" size=42,2>
<br>
Enter input for the C sample and click <input type="SUBMIT" value="ENTER">
<p>The output will be a screen with the text,
"YourInput=" followed by the text you typed above.
The contents of environment variable SERVER_SOFTWARE is also displayed.
</form>
</body>
</html>

When the url is requested the following page is displayed.

sampleC

Sample C input page


The Server needs to know what to do with the request so we have to redirect the request from the Linux Server to the IBM i server using the ProxyPass capabilities. You will notice from the code above that we are using the POST method from the form submission and we are going to call ‘/cgi-bin/samplec.exe’. This will be converted on the target system to our program call. The following changes were made to the Linux Apache configs and the server was restarted.

ProxyPreserveHost On
ProxyPass /cgi-bin/ http://192.168.200.61:8081/cgi-bin/
ProxyPassReverse /cgi-bin/ http://192.168.200.61:8081/cgi-bin/

This allows the Linux Server to act as a gateway to the IBM i Apache server, the client will see the response as if it is from the Linux server.
When we add the information into the input field on the page and press submit the following is displayed on the page.
samplec-out

Output from CGI program

Note:
Those reading carefully will notice the above page shows a url of www1.phptst.shield.local not www.phpest.shield.local as shown in the output screen below. This is because we also tested the iAMP server running on another IBM i to link to the same IBM Apache Server used in the Linux test using exactly the same code.

This is a useful setup for being able to keep existing CGI programs which are being presented via the IBM Apache Server while you migrate to a new PHP based interface. I would rather have replaced the entire CGI application for the clients with a newer and better PHP based interface, but the clients just wated a simple and quick fix, maybe we will get the opportunity to replace it later?

Note:-
The current version of iAMP which available for download from the Aura website does not support mod_proxy so if this is something you need to implement let us know and we can supply a version which contains the mod_proxy modules. I hope Aura will update the download if sufficient people need the support which will cut us out of the loop.

If you need assistance creating PHP environments for IBM i let us know. We have a lot of experience now with setting up PHP for IBM i and using the Easycom toolkit for access IBM i data and objects.

Chris…