Yort.Eftpos.Verifone.PosLink

An unofficial .Net implementation of the Verifone PosLink protocol version 2.2 for EFTPOS pinpads

Status

Supported Platforms

Currently;

• .Net Standard 2.0
  • Includes Xamarin.iOS, Xamarin.Android, .Net Core 2.0 and .Net 4.71
• .Net 4.5+
• UWP 10+ (Windows 10 Universal Programs, v10240 and up)

Supported Features

• Standard financial transactions
  • Purchase with or without cash out
  • Manual purchase (for PCIDSS compliance, cannot provide card details programmatically, must be entered on pinpad)
  • Cash out (only)
  • Manual cash out
  • Refund
  • Manual refund (for PCIDSS compliance, cannot provide card details programmatically, must be entered on pinpad)
• Common admin functions
  • Logon
  • Settlement Enquiry
  • Settlement Cutover
  • Reprint Last Receipt
  • Print (with optional reset) totals
• Poll request (device status)
• Cancel transaction
• Query card
• Ask responses (don't think these are used anymore but they have been implemented)

Unsupported Features

• All tip related transactions (advised these are obsolete)
• Cheque Authorisation (advised these are obsolete)
• All tab related transactions (unknown if these are obsolete or not)
• PRN messages (host printing)
• Host comms

Adding missing messages, where still supported by current protocol and hardware, should be fairly easy.

Getting Started

Install the Nuget package like this;

    PM> Install-Package Yort.Eftpos.Verifone.PosLink

There is a secondary project/Nuget package for Windows Forms based projects which will provide default user interface and prompts during a transaction (you can build your own, but this saves you having too if you're ok with the UI style provided).

    PM> Install-Package Yort.Eftpos.Verifone.PosLink.WinForms

Sample Pseudo-Code

The general pattern for implementing EFTPOS intergations is;

1. Persist your current request details to non-volatile storage. The request must be recoverable in the event of an unexpected failure (power cut/blue screen etc).
2. Begin the request
3. Process the result into your transaction model/complete the transaction or persist the result to storage.
4. Clear the persisted request details.

On start up, you must;

1. Check for a persisted request and if found;
   • Resend the request to the device using the PinpadClient.RetryRequest method. The request details must be the same as the last request sent.
   • Continue from step 3 above.
2. If not, send a poll request to check the device state.

You must also handle exceptions from the library when making requests;

• A TransactionFailureException represents a critical failure to obtain a result from the pinpad, as per the POS Link specification. You should prompt the user to either retry, or manually check the pinpad and choose an accepted/declined response manually.
• A PinPadConnectionException indicates the request was never sent to the pinpad because a connection could not be established. The request can be retried or treated as failed. The user should be advised to check the pinpad connection, network address etc.
• ArgumentException and derived exception types indicate invalid data in the request object (and the request was not sent).

// Sample code for making a purchase request
private async void EftposPurchaseButton_Click(object sender, EventArgs e)
{
    var request = new Yort.Eftpos.Verifone.PosLink.PurchaseRequest()
    {
        Amount = 10.00M,
    };

    SaveCurrentRequest(request);

    var pinpad = new Yort.Eftpos.Verifone.PosLink.PinpadClient("10.10.10.118");
    //This event handler attached here should update the status on screen. 
    pinpad.DisplayMessage += Pinpad_DisplayMessage;
    //The event handler attached here should prompt the user for a response to the query passed in the event arguments.
    pinpad.QueryOperator += Pinpad_QueryOperator; 

    try
    {
        var response = await pinpad.ProcessRequest<Yort.Eftpos.Verifone.PosLink.PurchaseRequest, Yort.Eftpos.Verifone.PosLink.PurchaseResponse>(request);

        bool paymentAccepted = response.ResponseCode == Yort.Eftpos.Verifone.PosLink.ResponseCodes.Accepted;
        ProcessResponse(paymentAccepted, response);
    }
    catch (Yort.Eftpos.Verifone.PosLink.TransactionFailureException)
    {
        //Prompt user to retry or manually provide result
    }
    catch (Yort.Eftpos.Verifone.PosLink.PosLinkConnectionException)
    {
        //Failed, treat as declined/failed, or prompt user to retry.
    }
    catch (ArgumentException)
    {
        //Something is wrong with the request, inform user.
    }
    finally
    {
        ClearCurrentRequest(request);
    }
}

// Code similar to this should run at startup
public async Task RecoverEftposResult()
{
    var request = RecoverCurrentRequest();
    if (request == null) return;

    var pinpad = new Yort.Eftpos.Verifone.PosLink.PinpadClient("10.10.10.118");
    //This event handler attached here should update the status on screen.
    pinpad.DisplayMessage += Pinpad_DisplayMessage;
    //The event handler attached here should prompt the user for a response to the query passed in the event arguments.
    pinpad.QueryOperator += Pinpad_QueryOperator;

    try
    {
        var response = await pinpad.RetryRequest<Yort.Eftpos.Verifone.PosLink.PurchaseRequest, Yort.Eftpos.Verifone.PosLink.PurchaseResponse>(request);

        bool paymentAccepted = response.ResponseCode == Yort.Eftpos.Verifone.PosLink.ResponseCodes.Accepted;
        ProcessResponse(paymentAccepted, response);
    }
    catch (Yort.Eftpos.Verifone.PosLink.TransactionFailureException)
    {
        //Prompt user to retry or manually provide result
    }
    catch (Yort.Eftpos.Verifone.PosLink.PosLinkConnectionException)
    {
        //Failed, treat as declined/failed, or prompt user to retry.
    }
    catch (ArgumentException)
    {
        //Something is wrong with the request, inform user.
    }
    finally
    {
        ClearCurrentRequest(request);
    }
}

// For Windows Forms you can import the *Yort.Eftpos.Verifone.PosLink.WinForms* Nuget package, 
// and use it to aid with the UI prompts/progress display. Create a 'DialogAdapter' instance
// and pass the pinpad client to it. It will attach to the pinpad client events and automatically 
// show dialogs as required during an EFTPOS request.
// A new DialogAdapter should be created for each request. Dispose the adatper after the response
// is returned to hide the dialog.

Yort.Eftpos.Verifone.PosLink.PurchaseResponse response = null;
using (var dialogAdapter = new Yort.Eftpos.Verifone.PosLink.DialogAdapter(pinpad, null, false))
{
    response = await pinpad.ProcessRequest<Yort.Eftpos.Verifone.PosLink.PurchaseRequest, Yort.Eftpos.Verifone.PosLink.PurchaseResponse>(request);

    bool paymentAccepted = response.ResponseCode == Yort.Eftpos.Verifone.PosLink.ResponseCodes.Accepted;
}
ProcessResponse(paymentAccepted, response);