Network Programming in .NET

0.4 + 0.4 = 0.79 … well done! 

Jokes aside, this is an example of how to use machine learning in C# to predict sequences, in this case to say the sequence of two inputs should result in the sum of the two inputs.

TLDR; the Github repo is here : https://github.com/infiniteloopltd/SharpML-Recurrent

It is 99.9% based on Andrew Fry’s code, but I have modified the dataset generator, that instead of modelling an XOR gate, it models a simple adder. I noticed that the values have to be between 0 and 1, but I guess, you just shift your range to that.

private static List<DataSequence> GetTrainingData()
{

var result = new List<DataSequence>();
for (var a = 0.0; a < 0.5; a += 0.1)
{
for (var b = 0.0; b < 0.5; b += 0.1)
{
var sum = a + b;
result.Add(new DataSequence(new List<DataStep>() { new DataStep(new[] { a, b }, new[] { sum }) }));
}
}

return result;
}

This simply provides a dataset of every combination of numbers in 0.1 increments between 0 and 0.5, and indicates the sum.

Obviously this training data can be improved, but it’s just a proof of concept, as you can imagine!

Next step is to add another dimension to the output. But that’s work for another day!

If you would like to learn about SQL server indexes, and SQL server performance in general, but can’t get your hands on a large dataset that really tests the limits of your SQL server, then here is a script that generates a huge dataset, based on random data.

create table Test1
(
id int identity(1,1),
guid varchar(36) default newid(),
dateCreated datetime default getdate(),
number float default rand()
)

while 1=1
Begin
insert into Test1 default values
end

You just let it run for as long as you like, then stop it whenever you have enough rows.

You can do very basic string matching using the LIKE operator in SQL server, but you quickly hit the limits of what you can easily do using the simple operations supported. .NET offers full Regex (Regular expression) support, and you can use this within SQL server by creating a UDF CLR (User defined function).

TL;DR; here is the Github repo: https://github.com/infiniteloopltd/SQLServerRegex

Which defines this one function;

using System.Data.SqlTypes;
using RX = System.Text.RegularExpressions;

public partial class UserDefinedFunctions
{
[Microsoft.SqlServer.Server.SqlFunction]
public static SqlString Regex(string input, string regex)
{
var match = RX.Regex.Match(input, regex).Groups[1].Value;
return new SqlString (match);
}
}

Which you can install into your SQL server database as follows;

EXEC sp_changedbowner ‘sa’
ALTER DATABASE [<your database here>] SET trustworthy ON

sp_configure ‘show advanced options’, 1;
GO
RECONFIGURE;
GO

sp_configure ‘clr enabled’, 1;
GO
RECONFIGURE;
GO

CREATE ASSEMBLY [DbRegex] AUTHORIZATION [dbo]
FROM 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WITH PERMISSION_SET = UNSAFE

CREATE FUNCTION [dbo].[regex] (@text [nvarchar](MAX), @regex [nvarchar](MAX))
RETURNS [nvarchar](MAX)
AS EXTERNAL NAME [DbRegex].[UserDefinedFunctions].[Regex]

Once that’s done, then you can run SQL commands like;

select dbo.regex(‘1234abc123′,’\d+([a-z]+)\d+’)

My disclaimer is that I don’t speak greek, and this code is far from a perfect transliteration from english to greek, but it’s a good starting point I guess.

It transliterates English to Greek; in a SQL UDF

create function Transliterate (@english nvarchar(max))
returns nvarchar(max)
as
begin
set @english = replace(@english,N’th’,N’θ’)
set @english = replace(@english,N’ch’,N’χ’)
set @english = replace(@english,N’ps’,N’ψ’)
set @english = replace(@english,N’q’,N’κο’)
set @english = replace(@english,N’w’,N’ου’)
set @english = replace(@english,N’a’,N’α’)
set @english = replace(@english,N’b’,N’β’)
set @english = replace(@english,N’c’,N’χ’)
set @english = replace(@english,N’v’,N’β’)
set @english = replace(@english,N’g’,N’γ’)
set @english = replace(@english,N’d’,N’δ’)
set @english = replace(@english,N’e’,N’ε’)
set @english = replace(@english,N’z’,N’ζ’)
set @english = replace(@english,N’i’,N’η’)
set @english = replace(@english,N’k’,N’κ’)
set @english = replace(@english,N’l’,N’λ’)
set @english = replace(@english,N’m’,N’μ’)
set @english = replace(@english,N’n’,N’ν’)
set @english = replace(@english,N’x’,N’ξ’)
set @english = replace(@english,N’o’,N’ο’)
set @english = replace(@english,N’p’,N’π’)
set @english = replace(@english,N’r’,N’ρ’)
set @english = replace(@english,N’s’,N’σ’)
set @english = replace(@english,N’t’,N’τ’)
set @english = replace(@english,N’y’,N’υ’)
set @english = replace(@english,N’h’,N”)
set @english = replace(@english,N’j’,N’ι’)
set @english = replace(@english,N’f’,N’φ’)
set @english = replace(@english,N’u’,N’υ’)
return @english
end

The AWS CLI allows you to interact with AWS from the command line, and an obvious use of the tool, is to upload your Database Backups to S3, to keep them safe.

Once you’ve configured AWS to run from the command line on your server, and tested it, then you try the exact same command from xp_cmdshell and it fails with “unable to locate credentials“.

What is happening here, is your remote desktop user, is probably “Adminstrator” but SQL server agent runs under the username MSSQLSERVER

You can verify the username used by SQL server agent by runing the command

xp_cmdshell ‘echo %username%’

The AWS CLI is looking for the configuration file under c:\users\MSSQLSERVER\.aws – but the configuration file is actually under c:\users\Adminstrator\.aws , so you need to copy the configuration file using xp_cmdshell as follows

1. Using remote desktop, copy the configuration file to an accessible folder, like C:\temp
2. xp_cmdshell ‘md C:\users\MSSQLSERVER\.aws’

   xp_cmdshell ‘copy c:\temp\credentials c:\users\MSSQLSERVER\.aws’

    

3. And then test with
   xp_cmdshell ‘”C:\Program Files\Amazon\AWSCLI\bin\aws.exe” s3 ls’

Google sheets is an amazing product, but let’s imagine, you’d like to expand upon Google Sheets to fill in the details of a cell by calling an API.

In this example, we’re using an API that determines the make and model of a car from it’s license plate, If you’d like to follow along, then you can create your own free account at https://www.regcheck.org.uk  – The username and password for this particular API have been removed from the demo code, you’ll need to use your own.

So, Open Google Sheets, and Press Tools -> Script Editor, then enter the following script;

function RegCheck(RegistrationNumber) {
var encode = Utilities.base64Encode(‘***USERNAME***:***PASSWORD***’, Utilities.Charset.UTF_8);
var option = {
headers : {
Authorization: “Basic “+ encode
}
}

var url = “https://www.regcheck.org.uk/api/json.aspx/Check/&#8221; + RegistrationNumber;
var response = UrlFetchApp.fetch(url, option).getContentText()
response = JSON.parse(response);

return response.Description;
}

What this does, is that it first creates the basic authenticatio header from your username and password, which you used to register with the API. And then passes the registration Number into the URL.

Once the URL returns, we extract the Description from the JSON returned, and return it back to Google Sheets.

Now, In google Sheets, all you need to do is enter =RegCheck(“xxxxx”) in a cell in order to call the API.  Where “RegCheck” is the function name

Of course, you can use the same approach to call any API you wanted.

If you ever need to generate a Uint8Array to represent a 1×1 pixel transparent PNG in Node, here’s the script

var base64 = “iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNkYAAAAAYAAjCB0C8AAAAASUVORK5CYII=”;
var atob = require(‘atob’);
var raw = atob(base64);
var rawLength = raw.length;
u8 = new Uint8Array(new ArrayBuffer(rawLength));
for(i = 0; i < rawLength; i++) {
u8[i] = raw.charCodeAt(i);
}

Two factor authentication is a way to level up your security, beyond username and password. Using Google Authenticator is also a great way to do this for free, since it doesn’t incur costs such as doing 2FA via SMS.

It does require a basic tech awareness, so if your typical user is elderly, then this is not the way to go.

You can of course use Google Authenticator without using an API, you can implement the crypto code yourself, but using this API at AuthenticatorAPI.com does save you alot of development time, since it’s just two API calls.

So, how does it work?, well first you have to generate a random code. This could be just any random code that comes to your head, or perhaps better, to generate a random code per user, and store this.

You now need to show a QR code to a user, which they scan into the Authenticator App. The QR code is generated using the API, and is just a block of HTML you display on your page. It’s 300×300 pixels in size.

To do this, you call;

https://www.authenticatorApi.com/pair.aspx?AppName=MyApp&AppInfo=John&SecretCode=12345678BXYT

Once the user has paired, and they go to log in, you prompt them for their pin. You then have to send the PIN and the SecretCode from earlier to our API, and it will return either True or False.

By Calling;

https://www.authenticatorApi.com/Validate.aspx?Pin=123456&SecretCode=12345678BXYT

The pin is time dependent, so the same PIN won’t work the following day. This defeats key loggers and replay attacks.

As an update for 2020, this code is going to get buried under ice in Svalbard, under Github’s archive program!

Latvia is a small baltic country, with a population of 1.92 million, and a car ownership rate of 342 per 1,000 – so an estimated car count of 650,000 vehicles. Today, we have expanded our API coverage to include Latvia, you can read more about this at our Latvian website http://www.autoapi.lv 

Car registration plates in Latvia use the /CheckLatvia  endpoint and return the following information:

• Make / Model
• Age
• VIN number
• Fuel
• Engine size
• Representative image

Sample Registration Number: 

GZ3425

Sample Json:

{

  “Description”: “VW BORA”,

  “Variant”: “BORA (1J2) (98-13)”,

  “RegistrationYear”: 1998,

  “CarMake”: {

    “CurrentTextValue”: “VW”

  },

  “CarModel”: {

    “CurrentTextValue”: “BORA”

  },

  “MakeDescription”: {

    “CurrentTextValue”: “VW”

  },

  “ModelDescription”: {

    “CurrentTextValue”: “BORA”

  },

  “VehicleIdentificationNumber”: “WVWZZZ1JZXW273563”,

  “EngineSize”: 2324,

  “Power”: 110,

  “FuelType”: “Benzīns”,

  “ImageUrl”: “http://autoapi.lv/image.aspx/@VlcgQk9SQQ==&#8221;

}

The UK have a very open attitude to their Company registration data, they have bulk data downloads, and a very open API that allows you to read lots of public domain data about UK companies. This is an example in C# that uses this API to return a list of officers (Board memebers) of a UK company, given a UK company number.

private static List GetOfficers(string companyNumber)
{
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
var strUrl = “https://api.companieshouse.gov.uk/company/{0}/officers”;
strUrl = string.Format(strUrl, companyNumber);
var credentials = Convert.ToBase64String(Encoding.ASCII.GetBytes(“xxxxxxxx:”));
var wc = new WebClient();
wc.Headers[HttpRequestHeader.Authorization] = string.Format(“Basic {0}”, credentials);
try
{
var strResult = wc.DownloadString(strUrl);
var jResult = JObject.Parse(strResult);
return jResult[“items”].Select(jOfficer => new Officer(jOfficer)).ToList();
}
catch (WebException ex)
{
var resp = new StreamReader(ex.Response.GetResponseStream()).ReadToEnd();
Console.WriteLine(resp);
return null;
}
}

You will need your own API key, and change the “xxxxxxxx” in the code above. Also, you’ll need to implement your own Officer class, which is outside the scope of this example.