Develop Reference

How to store data through web service when data coming to my serial port will be asynchronous?

I have one device "installed" on a users desk (a desk is nothing but a chair or table on which user will sit), and I will be supporting thousands of desks.
A user will have one "chip" and the user will scan this chip on the device which is installed on their desk.
The device will read the data off the chip and will send it to my laptop which will also have one of the devices installed, except this device is the main device responsible for collecting all user scan chip data.
All the data will be routed to my device via a wifi router and I will listen to this from my Main device and read data from this device from my laptop via serial port connection.
This data sending will happen as each user number scans his/her chip.
I have created a windows form application which will continuously run in the background on my laptop, and will be listening to my serial port on which main device is connected.
This is my code taken from here: Source Code Reference:
public partial class MainUI : Form
{
SerialPortManager _spManager;
public MainUI()
{
InitializeComponent();
UserInitialization();
}
}
private void UserInitialization()
{
_spManager = new SerialPortManager();
_spManager.NewSerialDataRecieved += new EventHandler<SerialDataEventArgs>(_spManager_NewSerialDataRecieved);
this.FormClosing += new FormClosingEventHandler(MainUI_FormClosing);
}
private void MainUI_Load(object sender, EventArgs e)
{
_spManager.StartListening()
}
void _serialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
int dataLength = _serialPort.BytesToRead;
byte[] data = new byte[dataLength];
int nbrDataRead = _serialPort.Read(data, 0, dataLength);
if (nbrDataRead == 0)
return;
// Send data to whom ever interested
if (NewSerialDataRecieved != null)
{
NewSerialDataRecieved(this, new SerialDataEventArgs(data));
}
}
void _spManager_NewSerialDataRecieved(object sender, SerialDataEventArgs e)
{
if (this.InvokeRequired)
{
// Using this.Invoke causes deadlock when closing serial port, and BeginInvoke is good practice anyway.
this.BeginInvoke(new EventHandler<SerialDataEventArgs>(_spManager_NewSerialDataRecieved), new object[] { sender, e });
return;
}
//data is converted to text
string str = Encoding.ASCII.GetString(e.Data);
if (!string.IsNullOrEmpty(str))
{
//Here i will store that data in to my database through web service.
//What i should use whether WCF service or Web Api because data will be continuos like at a
//time more than 10 or 100 user can scan data at the same time so this event will be fired continuously.
//I am using entity framework to store data in to my database and how to ansynchornously call web service to store my data
//so that my call doesnt block incoming data to serial port
}
}
My main concern is I will have numerous users who will scan data at the same time and how I will handle when more than 10 or 100 user scan the data at the same time.
How can I mitigate this potential issue?

Ok, if i got the question right you need to do something like this ...
void _serialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
int dataLength = _serialPort.BytesToRead;
byte[] data = new byte[dataLength];
int nbrDataRead = _serialPort.Read(data, 0, dataLength);
if (nbrDataRead == 0)
return;
// Send data to api
string str = Encoding.ASCII.GetString(e.Data);
if (!string.IsNullOrEmpty(str))
{
var api = new HttpClient();
api.BaseUrl("http://somewhere.com");
api.PostAsJsonAsync("api/Something", str)
}
if (this.InvokeRequired)
{
// Using this.Invoke causes deadlock when closing serial port,
// and BeginInvoke is good practice anyway.
this.BeginInvoke(new EventHandler<SerialDataEventArgs>(
_spManager_NewSerialDataRecieved), new object[] { sender, e
});
return;
}
}
// i think this can go completely ...
void _spManager_NewSerialDataRecieved(object sender, SerialDataEventArgs e)
That posts the data to webapi but whilst that post is taking place on another thread the serial port can carry on receiving data

close your serial port and load every some-amount-of-time. After that some-amount-of-time open the port and scan all devices, then close it again.
public void MainUI.Load(Object sender, Eventargs e)
{
if (_spmanager != null && !_spManager.IsOpen)
//*write the code here where it opens and starts listening
_spmanager.StartListening();
//*write the code here where it waits a little bit then
_spmanager.Close();
}
Therefore everytime it loads it starts when the port is closed, it opens for a little bit, scans whatever values are true and then closes again.
I am not very sure about this but it is just an idea of how to handle it. The code might not be accurate or currect I just wrote it quickly. Take the idea from this

Enumerating IPP Printers

I'm looking into DNS based service discovery in Windows 10 and found this video from Build. The only change I made to discovery was changing the service name to "_ipp._tcp". However I don't get any hits even though I know I have > 15 IPP enabled printers on the network (I can successfully identify these using the ipptool, IOS and Android code).
I've checked and double checked for typos. I've included all networking capabilities in the appxmanifest file.
Here's my code, pretty straight forward:
public sealed partial class MainPage : Page
{
static Guid DnsSdProtocol = new Guid("{4526e8c1-8aac-4153-9b16-55e86ada0e54}");
string queryString = "System.Devices.AepService.ProtocolId:={" + DnsSdProtocol + "} AND " +
"System.Devices.Dnssd.Domain:=\"local\" AND System.Devices.Dnssd.ServiceName:=\"_ipp._tcp\"";
DeviceWatcher watcher;
public MainPage()
{
this.InitializeComponent();
}
private void button_Click(object sender, RoutedEventArgs e)
{
watcher = DeviceInformation.CreateWatcher(queryString,
new String[]
{
"System.Devices.Dnssd.HostName",
"System.Devices.Dnssd.ServiceName",
"System.Devices.Dnssd.TextAttributes",
"System.Devices.IpAddress" },
DeviceInformationKind.AssociationEndpointService
);
watcher.Added += Watcher_Added;
watcher.Start();
}
private void Watcher_Added(DeviceWatcher sender, DeviceInformation args)
{
System.Diagnostics.Debug.WriteLine("found device");
}
}
Does anybody else have experience with this and can help figure out why no devices are found? Is my query correct? Do I need to do anything else when setting up the DeviceWatcher?
update
I've verified the requests are being created since they are showing up in Wireshark. They look to be identical to other mdns requests being created. I've also verified I can create SSDP requests that return discovered devices so I doubt it's an issue with networking permissions via app capabilities.

Try using the watcher.Updated handler. Even if it is empty, the presence of an Updated handler can cause the Added handler to be triggered.

Checking device status, while receiving data from serial port c#

Life status of device connected via serial port.
Hello everyone.
How can I check if the device responds to the request? I'm googling this for couple days and tried lot of solutions also from SO, but nothing gave me results that I've expected. After lot of tries I'm in point described below. I think I'm very close but now I need little help, so thanks for every answer in advance.
The current situation
What am I doing right now is very simple. First of all I'm opening serial port serialPort.Open() at very beggining of app (data is receiving almost all the application running time).
As this is just an example in my form is only one label called labelStatus and labelStatus.Text = "Not connected"
Next I'm adding a timer and it's tick method, that contains execute of serialPort.Write(). Timer Interval is set to 100 if that matters.
private void timer_Tick(object sender, EventArgs e)
{
if (serialPort.IsOpen)
{
serialPort.WriteLine("r"); //I'm sending "r" message and device send data back
}
}
Next step is create DataReceived event like below (very simplified version, in my app received data is parsing to floats and storing in array, but it's just to show the problem)
private void serialPort_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
string someVariable = serialPort.ReadLine();
labelStatus.Invoke((MethodInvoker)(() => labelStatus.Text = "Connected"));
//If i received something that means the device is plugged in and connection is correct (still very simplified)
}
One last thing is create ErrorReceived method.
private void serialPort_ErrorReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
labelStatus.Invoke((MethodInvoker)(() => labelStatus.Text = "Not connected"));
}
Untill now everything works brilliant. Sending data works. DataReceived event is executig each 100 miliseconds when data is send. My data is received properly with no problems. When I start application labelStatus text is "Not connected" (device cable is not plugged in). When I plugged in device labelStatus text changing to "Connected". But now when I plugged of cable ErrorReceived event is not executing and labelStatus text is still "Connected". So as I've asked before: How can I check is device still connected to computer? (Or maybe: how to execute ErrorReceived event, when data is not receiving?).
Note: Serial port ReadTimeout is set to 300 miliseconds.
What have I tried
I've tried lot of things but this one in my head seems to should work but doesn't.
I've modified DataReceived event and I've put serialPort.ReadLine() into try/catch block with TimeoutException where I've tried to manually execute ErrorReceived method like below
private void serialPort_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
try
{
string someVariable = serialPort.ReadLine();
labelStatus.Invoke((MethodInvoker)(() => labelStatus.Text = "Connected"));
//If i received something that means the device is plugged in and connection is correct (still very simplified)
}
catch (TimeoutException)
{
serialPort_ErrorReceived(null, null);
}
}
I was hoping that will work like I want.
BTW. Sorry for my English. It's not perfect, but I do my best. Cheers!

Listen to the WM_DEVICECHANGE event that will be fired when a device is removed or inserted.
Here is an example of a implementation and some more information:
Detect serial port insertion/removal
http://www.codemiles.com/download/file.php?id=719 (USB Sample)
http://msdn.microsoft.com/en-us/library/windows/desktop/aa363480(v=vs.85).aspx

This is solution in my case
Regarding to Martjin's answer i need to further explain my situation. First of all I want to say that I'm not installing any hardware into my computer, so in my opinion WM_DEVICECHANGE event was not what i need (but of course thanks for information, I've learned something new). Application is reading data from scale. Scale after plug into com port is not sending any data and actually there's no communication between it and computer at all. The only way to read data is to send request to scale, so I have to rely on that.
First try
The plan:
Add two static int fields (flags) checkOld and checkNew,
increment checkNew in DataReceived, check in timer Tick method
is checkOld is equal to checkNew. If true that means checkNew
was not increment, and that means DataReceived was not executed.
`
private void serialPort_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
checkNew++;
string someVariable = serialPort.ReadLine();
labelStatus.Invoke((MethodInvoker)(() => labelStatus.Text = "Connected"));
//If i received something that means the device is plugged in and connection is correct (still very simplified)
}
private void timer_Tick(object sender, EventArgs e)
{
if (serialPort.IsOpen)
{
serialPort.WriteLine("r"); //I'm sending "r" message and device send data back
}
if (checkOld == checkNew)
{
labelStatus.Invoke((MethodInvoker)(() => labelStatus.Text = "Not connected"));
}
}
`
The plan was good but when I've tested it result was not even good. What happened? Actually device status was blinking connected-not connected-connected-not connected etc. I've wrote some data to output and get answer. The timer was looping so fast that DataReceived event could not always increment checkNew value.
Final solution
Based on what I had at the moment I've decided to add some little changes. Instead of comparing two integers values try to collect couple last values ad check if all were the sem or not.
The plan:
Add three static fields: first six elements array of integers
statusArray, second integer index with value equals to 6 (last
element of array + 1), third integer checkNew,
increment checkNew in
DataReceived event,
in timer Tick event fill array to index,
decrement index value untill whole array is filled, and if index == 0 reset index value to
6,
and last check if last six values of checkNew, stored in
statusArray are the same. If true that means DataReceived did not
executed six times in a row, and now I can be sure that connection is
lost.
`
static int index = 6;
static int checkNew = 0;
static int[] statusArray = {0,0,0,0,0,0};
private void serialPort_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
checkNew++;
string someVariable = serialPort.ReadLine();
labelStatus.Invoke((MethodInvoker)(() => labelStatus.Text = "Connected"));
//If i received something that means the device is plugged in and connection is correct (still very simplified)
}
private void timer_Tick(object sender, EventArgs e)
{
if (serialPort.IsOpen)
{
serialPort.WriteLine("r"); //I'm sending "r" message and device send data back
}
if (index == 0)
index = 6;
index--;
int value = statusArray[index] = checkNew;
}
`

Getting GPS Coordinates Windows Phone 7

I've been looking quite some time today to gather GPS coordinates from a Windows Phone 7 device - however since I do not have an actual test device here I tried to set some dummy data which I want to have returned instead of real GPS Data ... that, however ist not working out too well:
This code ist partially an example from so which I found here. However I tried to put it into a class which I can access later.
public class GetGPS : GeoCoordinateWatcher
{
GeoCoordinateWatcher watcher;
public GetGPS()
{
watcher = new GeoCoordinateWatcher(GeoPositionAccuracy.Default);
watcher.MovementThreshold = 20;
watcher.PositionChanged += this.watcher_PositionChanged;
watcher.StatusChanged += this.watcher_StatusChanged;
watcher.Start();
}
private void watcher_StatusChanged(object sender, GeoPositionStatusChangedEventArgs e)
{
switch (e.Status)
{
case GeoPositionStatus.Ready:
//plingpling
break;
case GeoPositionStatus.Disabled:
// location is unsupported on this device
break;
case GeoPositionStatus.NoData:
watcher.Position.Location.Latitude = 54.086369f;
watcher.Position.Location.Longitude = 12.124754f;
break;
}
}
private void watcher_PositionChanged(object sender, GeoPositionChangedEventArgs<GeoCoordinate> e)
{
var epl = e.Position.Location;
// Access the position information thusly:
epl.Latitude.ToString("0.000");
epl.Longitude.ToString("0.000");
epl.Altitude.ToString();
epl.HorizontalAccuracy.ToString();
epl.VerticalAccuracy.ToString();
epl.Course.ToString();
epl.Speed.ToString();
e.Position.Timestamp.LocalDateTime.ToString();
}
}
This is my other class in which I try to access the data - however I always get NaN as lat1Rad and long1Rad ... can you please help me?
I want that example to be functional on the emulator ( with a fixed GPS Coordinate ) and on a phone 7 device - where it actually grabs the value.
GetGPS location1= new GetGPS();
//GeoCoordinate myPosition = location1.getPosition();
//Radianten berechnen
double lat1Rad = GradZuRad(location1.Position.Location.Latitude);
double long1Rad = GradZuRad(location1.Position.Location.Longitude);
I basically just want to program a class which returns me the CURRENT GPS Position.

Where is your example code from?
Have you tried using the sample on MSDN?
Alternatively, there's a greate simulator available from http://phone7.wordpress.com/2010/08/02/no-device-no-gps-no-matter-with-code/

Why are you deriving frmo GeoCoordinateWatcher? That's a mistake, IMO. It makes it unclear when you're using the members of your own class and when you're using the delegated instance. At the moment you're setting the coordinates on the delegated watcher, but then asking for the coordinates from the GetGPS instance directly.
I suggest you implement IGeoPositionWatcher<GeoCoordinate> with your own "fixed" position watcher - and then decide at execution time whether to use that or the real GeoCoordinateWatcher. Obviously this means your client code should only depend on IGeoPositionWatcher<GeoCoordinate> instead of GeoCoordinateWatcher directly. This should also help for unit testing purposes.

Of course Jon's answer is very apropos - I think you've not done reasonable interface abstraction, but even when you get that, for simulated data have you taken a look at Kevin Wolf's GPS Simulator for Windpws Phone?

Simple C# Screen sharing application

I am looking to create a very basic screen sharing application in C#. No remote control necessary. I just want a user to be able to broadcast their screen to a webserver.
How should I implement this? (Any pointer in the right direction will be greatly appreciated).
It does NOT need to be high FPS. Would be sufficient to even update ever 5s or so. Do you think it would be sufficient to just upload a screenshot ever 5 seconds to my web server?

I previously blogged about how remote screen sharing software works here, it is not specific to C# but it gives a good fundamental understanding on the topic. Also linked in that article is the remote frame buffer spec which you'll also probably want to read up on.
Basically you will want to take screenshots and you can transmit those screenshots and display them on the other side. You can keep the last screenshot and compare the screenshot in blocks to see which blocks of the screenshot you need to send. You would typically do some sort of compression before sending the data.
To have remote control you can track mouse movement and transmit it and set the pointer position on the other end. Also ditto about keystrokes.
As far as compression goes in C#, you can simply use JpegBitmapEncoder to create your screenshots with Jpeg compression with the quality that you want.
JpegBitmapEncoder encoder = new JpegBitmapEncoder();
encoder.QualityLevel = 40;
To compare file blocks you are probably best to create a hash on the old block and the new one, and then check to see if they are the same. You can use any hashing algorithm you want for this.

Here's code to take a screenshot, uncompressed as a bitmap:
public static Bitmap TakeScreenshot() {
Rectangle totalSize = Rectangle.Empty;
foreach (Screen s in Screen.AllScreens)
totalSize = Rectangle.Union(totalSize, s.Bounds);
Bitmap screenShotBMP = new Bitmap(totalSize.Width, totalSize.Height, PixelFormat.
Format32bppArgb);
Graphics screenShotGraphics = Graphics.FromImage(screenShotBMP);
screenShotGraphics.CopyFromScreen(totalSize.X, totalSize.Y, 0, 0, totalSize.Size,
CopyPixelOperation.SourceCopy);
screenShotGraphics.Dispose();
return screenShotBMP;
}
Now just compress it and send it over the wire, and you're done.
This code combines all screens in a multiscreen setup into one image. Tweak as needed.

Well, it can be as simple as taking screenshots, compressing them, and then sending them over the wire. However, there is existing software that already does this. Is this for practice?

I'm looking to do something similar, and I just found this up on CodeProject. I think this will help you.
http://www.codeproject.com/Articles/371955/Motion-JPEG-Streaming-Server

The key player on sharing/replicating a screen is a COM Component called: RPDViewer
Add that com component to your window form and in References as well..
and thin add this code to your form load and you will get the screen replicated in your form:
using RDPCOMAPILib;
using System;
using System.Windows.Forms;
namespace screenSharingAttempt
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
RDPSession x = new RDPSession();
private void Incoming(object Guest)
{
IRDPSRAPIAttendee MyGuest = (IRDPSRAPIAttendee)Guest;
MyGuest.ControlLevel = CTRL_LEVEL.CTRL_LEVEL_INTERACTIVE;
}
//access to COM/firewall will prompt
private void button1_Click(object sender, EventArgs e)
{
x.OnAttendeeConnected += Incoming;
x.Open();
}
//connect
private void button2_Click(object sender, EventArgs e)
{
IRDPSRAPIInvitation Invitation = x.Invitations.CreateInvitation("Trial", "MyGroup", "", 10);
textBox1.Text = Invitation.ConnectionString;
}
//Share screen
private void button4_Click(object sender, EventArgs e)
{
string Invitation = textBox1.Text;// "";// Interaction.InputBox("Insert Invitation ConnectionString", "Attention");
axRDPViewer1.Connect(Invitation, "User1", "");
}
//stop sharing
private void button5_Click(object sender, EventArgs e)
{
axRDPViewer1.Disconnect();
}
}
}