Showing posts with label remoteobject. Show all posts
Showing posts with label remoteobject. Show all posts

Tuesday, September 8, 2009

Putting available ports to use with AMF

In a previous post, see a detailed a procedure to choose and make available a tcp/alt port on a web server to avail the use of asynchronous data services. That post leads to this one, in which AMF calls are made over the available port.

To start, here is a method to test the port for an http response using netcat, via stearns.org:
echo -e "GET http://yoursite.com HTTP/1.0\n\n" | nc yoursite.com 80 | less
...or using the alternate available port...
echo -e "GET http://yoursite.com HTTP/1.0\n\n" | nc yoursite.com 8080 | less
This is a good example of using netcat as a client to get a response from an http service.

Analogous to this is the stated goal of this post, establishing connectivity between a lightweight client and an AMF service. Does that service by definition reside on an HTTP gateway? What type of gateway is the service? That remains to be answered.

For now, note that there is a starting example available from pyamf.com that allows you to test a connection to a third-party HTTP gateway. Titled PyAMF AMF Client, it works in the following manner to establish a simple methodology.
  1. In SSH, launch a python command line
  2. Load the modules in pyamf to initiate a test
  3. Request the remote service and look for a successful response
Here, copied from the pyamf.com example, is the applicable sequence
from pyamf.remoting.client import RemotingService

client = RemotingService('http://demo.pyamf.org/gateway/recordset')
service = client.getService('service')

print service.getLanguages()
...which should directly result in the following response from pyamf.com
<pyamf.amf0.recordset><pyamf.amf0.recordset></pyamf.amf0.recordset></pyamf.amf0.recordset>
Why does this work as it should? Some of the reasons why it works

pyamf.remoting.client.RemotingService (see API)


We instantiated the class RemotingService, the instance call of which includes a parametric reference to an available gateway. Once you provide a valid gateway address, you have established a client for AMF calls.


getService method


The method parameter is the name of a service, in this case the service defined at http://demo.pyamf.org/gateway/recordset/. Try browsing to this address and you will see


400 Bad Request

To access this PyAMF gateway you must use POST requests (GET received)

The gateway provides information that it is a PyAMF gateway and only accepts POST requests. If you use netcat to contact the gateway...


echo -e "GET http://demo.pyamf.org/gateway/recordset HTTP/1.0\n\n" | nc demo.pyamf.org 80 | less

...you will get a similar response. If you netcat a POST to the gateway, you will get this...

HTTP/1.1 500 Internal Server Error
Date: Wed, 09 Sep 2009 15:21:18 GMT
Server: Apache/2.0.55 (Ubuntu) DAV/2 SVN/1.5.6 mod_python/3.3.1 Python/2.5.4 mod_wsgi/2.4 PHP/5.1.2 mod_ssl/2.0.55 OpenSSL/0.9.8a mod_perl/2.0.2 Perl/v5.8.7
Content-Length: 534
Connection: close
Content-Type: text/html; charset=iso-8859-1

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>500 Internal Server Error</title>
</head><body>
<h1>Internal Server Error</h1>
<p>The server encountered an internal error or
misconfiguration and was unable to complete
your request.</p>
<p>Please contact the server administrator,
info@pyamf.org and inform them of the time the error occurred,
and anything you might have done that may have
caused the error.</p>
<p>More information about this error may be available
in the server error log.</p>
</body></html>

This is a longer response, but not a successful response. The question remains, how can a request to the server result in a service initiation? Let's look at some other possibilities.
Posted by at No comments:
Labels: , , , ,

Thursday, September 3, 2009

Simple Endpoint Test for Asynchronous Unit and Integration Processes

In the creation of open-source RIAs, it can be very difficult to ensure connectivity of endpoints. There are potential snags and edge cases surrounding the following critical points:
  • Security clearance of port
  • Availability of port resource
  • Conflicts between multiple running servers
  • Properly-declared URI endpoints
As in point three, matters can be complicated when proxy servers, such as lighttpd or nginx are working in conjunction with apache. Most likely, both are open on different IP registers on port 80; apache proxy on localhost, and the lightweight server on the public IP.

An RIA will asynchronously connect via a RemoteObject call on another port. It requires a valid connection. Utilities like netcat can save you from a quagmire of ineffectual random testing.

First, open the port in apache, as it will be the ORM-enabled server. Typically, the port is 8000 or 8080 for arbitrary reasons of convention and familiarity. Make sure your 8000 or 8080 is not tied up with memchache or some other port-requisite ancillary utility. Open up ports.conf and add the port in the configuration script.

TEST THE PORT

Restart the apache server. Using a port utility such as netcat, test port connectivity. One quick way is to use netcat from a command line. Netcat will attempt to connect to any port(s) you specify and report the protocol it encountered:

nc -v -w 2 -z target 20-30

FIREWALLS

Don't forget to modify your security settings to allow the port! Specifically, if you have set up a firewall, iptables requires an entry allowing public connections over the port in question or connections will fail. If they have been changed, be sure to restart the apache server and that the rules have been saved either via command-line or the initializing script, usually /etc/network/interfaces.

Be sure your apache server's NameVirtualHost settings allow the wildcard * and not only localhost connections. This way, requests from your http-alt port will bypass your proxy server altogether. Apache might warn you thus, but it can be ignored:

[Thu Sep 03 16:20:42 2009] [warn] NameVirtualHost *:80 has no VirtualHosts

With these potential obstructions addressed, you should be able to tunnel your way to fame and fortune.

NEXT UP

How to put that port to use in an RIA RemoteObject call.
Posted by at No comments:
Labels: , , , , ,
Subscribe to: Posts (Atom)