Some Basics

I had few emails asking some basic questions, and to make usefulness to everyone I'm posting my replies here along with the latest versions.

Well first of all, The HOST STATIC IP in the server configuration should not be "localhost".
Your magento installation is at your remote server(most probably) while your checkout installation is on your computer, what you're telling magento is to try to connect to the postgresql installed on the same machine as magento which is incorrect.

I highly suggest you try everything on your local machine.
A few tips on getting this host locally:

Make a backup of your magento store from System->Tools->Backups.
download it from your var/backups on your magento server.
Then compress your installation files to a zip file (you can skip the media folder coz it must be big and full of images), you can skip var/backups because it will be full of your database backups, and you can skip the downloader folder too.
Then host this magento installation on your computer (use MAMP, it's great).
use "Sequel Pro" to connect to magento's mysql database and make sure that you change core_config_data table the "base url" and "base secure url" to "localhost". if you don't do this, magento will not display properly on your browser because it will not be able to find its required files (css and images)

This way you can test further and be sure you will not break your real shop.

One thing to clear out. At the end, when you want to make the true connection with your live installation and your checkout installation, you must make sure the machine where checkout is installed does have a STATIC IP. This is a must so that your remote server will be able to find it and connect to it each time it needs. Or else you will not be able to work live.
Probably if you do not have STATIC IP, your ISP will charge your for it a little but not much.

The postgresql database you should be connecting to should be Checkout App's. And if everything's set to default when you first created Checkout App's DB then the port should be 5505. Also if Checkout is installed on your computer and your magento is installed on the same one then the host should be "localhost" or "127.0.0.1" depending on if connecting through socket or not.

Going to Administrate stores was meant to show you Checkout App's DB name so you put it in the configuration of the extension, but I was not in focus that time that I wrote the code to use the DB name set in the configuration...so to bypass this issue, put in the configuration DB name: postgres.

After you get the Administrate stores connecting to your server and retrieving your Checkout DB name, put it back in the config.
Administrate stores will also help you set your store order number.

If you go through this and you face other issues, send me back, i'll do my best to help you with your project.

Version 1.3.2Beta
http://www.megafileupload.com/en/file/240535/CheckoutAppSync-1-3-2-tgz.html

Beta 1.0.0 Release

Just done packaging newest Release.
Release submitted to Magento Connect and awaiting approval.

Fixed issues with installation and database tables creation.

Features:
-Customers sync/detect changes and update
-Tax rates sync
-Sync orders
-Sku, name, prices(and special price), cost, tax assigned for simple products
-Sync stock to checkoutapp (auto create a purchase order like checkoutapp's own products import from file feature)
-Sync variations to checkoutapp (product attributes in magento)
-Sync stock back to Magento
-A Sync Schedule for auto order push and auto import stock to update magento's
-Cron Jobs for automation(depends on the sync schedule)
-Update Order Info (print packingslip, shipping rate calculation)
-Aramex Shipping AirWayBill PDF creation

Download link: http://www.megafileupload.com/en/file/221551/MageCheckoutAppSync-1-0-0-tgz.html

Progress

Here's the progress so far:

-Customers sync/detect changes and update (done)
-Tax rates sync (done)
-Sync orders (done)
-Sku, name, prices, cost, tax assigned for simple products(done)
-Sync stock to checkoutapp (done...by auto create a purchase order like checkoutapp's own products import from file feature)
-Sync variations to checkoutapp (product attributes in magento) (done)
-Sync stock back to Magento (done)
-Automate these actions somehow, like with cron jobs or trigger after event (done...only implemented for auto order push and auto import stock to update magento's)
-Create a kind of log of each process/sync done for revising and error handling/fixing situations (done...only for the automated features, logs errors and success)

I'm planning to release a beta version asap, and a demo video.

Where am I - Roadmap

One thing I want to clear:
All my work is goin in the way of "syncing Magento TO Checkout App"...meaning my codes will not be as useful for those who already work on Checkout as for those who work on Magento and just want to add POS like me.

Concept is, sync tax, customers, products, stock and orders.
syncing orders will run the customers sync codes along the process to successfully assign the customer to the synced product with updated shipping addresses.
I already implemented the tax sync, but for me, in Egypt, we have only sales tax of 10%, no tax regions or any other special or compound rates...So I only implemented syncing the tax rate as a tax group in Checkout.

I am currently in the middle of coding the simple products sync.
The plan is to successfully implement :
-Customers sync/detect changes and update (done)
-Tax rates sync (done)
-Sync orders (partially done-without products or amounts)
-Sku, name, prices, cost, tax assigned for simple products(in progress)
-Sync stock to update inventory total costs and ledger
-Use of variations to sync configurable products and their associated simple products
-Sync stock back to Magento
-Automate these actions somehow, like with cron jobs or trigger after event
-Create a kind of log of each process/sync done for revising and error handling/fixing situations

I really am not finding hard time coding, and I really encourage people to start working with me on this module because in 10 days I am 30% done of what I need, so this is promising.
I also want to clear out that since I'm not just developing this for the community but first of all solve my work case. Then, not all features can be implemented in this module by me since I don't have the time, and I don't have the case to work on.

Maybe we can move this project on to bazaar or other similar project management solutions

Alpha 0.2.0 Release

New in this version:
-Real Magento Order Number is added to the order as a note. This makes searching for orders with Magento's # really easier from the orders list search bar.
-Sync Tax Rates from Magento to Checkout App. This is for simple tax rates, no tax regions.

Note: Complete Tax sync can be coded easily to implement all Magento's power, but for my project I am satisfied with syncing the simple tax rates. Feel free to improve the tax codings to adapt to your needs

Download Alpha 0.2.0

Alpha 0.1.0-Release

So far what I reached is complete customer sync to Checkout from orders.
You will be able to mass select orders, choose "Sync Orders" from the mass options, customer is then created/updated(update concept tested and is OK). Shipping addresses are checked and if the order's shipping address is not found it is created and assigned to the synced order.

No items, amounts or totals sync codes are written yet.

This release is just for curious people who want to really know if this project is doing fine :)
Comments and suggestions are very welcome.
enjoy :)
Download Alpha 0.1.0

Accessing CheckoutApp Database

At first, be sure you firewall your network to checkout's server or else you might have security risks. It is recommended to only forward TCP port 5505 on which Checkout's Postgres server is accessed and to enable access of WAN to only your Magento's host IP for extra security. In order for this Magento module to work, your Magento host server will have to be able to reach Checkout's server (normally this means to have server set on a static IP)

Locally, if you want to access Checkout's DB, first launch Checkout. The welcome window will show, and a loading wheel on the top right will indicate server is being started. Once server started open your preferred GUI Postgres Admin (like pgAdmin or Navicat).



When you setup a new store in Checkout, a 6 character Database Name is used, and non-related to the name you have set.
Checkout comes with a preset demo store...but let's just try to look at which databases are available on the server first.

Set in pgAdmin host as localhost (or any other adequate IP).
set port: 5505
username: admin
password: admin
set maintenance DB the default postgres

you should now be able to login.



Take note of the required DB name, we will need to input this in the module's configuration in Magento. (note that if you did not setup a new store, you should be able to see a DB already there which is the demo store)