Develop Reference

How do I send objects over a TCP stream?

I'm trying to set up an interface to send serialized objects between a client and a server using a TCP connection.
I have the following class and extension methods for reading and writing these objects from/to the stream:
public class NetworkTransmittedUpdate
{
/// <summary>
/// The type of update that is being sent
/// </summary>
public UpdateType UpdateType { get; init; }
/// <summary>
/// The type that UpdateObject should be deserialized as. Should match one of the types in SerializedTypes
/// </summary>
public string UpdateObjectType { get; init; } = string.Empty;
/// <summary>
/// Any information that accompanies the update. Each update type has an associated UpdateObject type, which is
/// usually but not always the same for both frontend and backend. UpdateObject may be null if only the event
/// happening must be conveyed.
/// </summary>
public object? UpdateObject { get; init; }
}
public static class StreamExtensions
{
/// <summary>
/// Attempts to read a serialized object from the stream, convert it, and return it
/// </summary>
/// <param name="stream">The stream to read from</param>
/// <typeparam name="T">The type of object to deserialize</typeparam>
/// <returns>An instance of the object, or null if it could not be created</returns>
public static T? ReadObject<T>(this Stream stream) where T : class
{
// Get length of incoming object
var sizeBuffer = new byte[sizeof(int)];
var bytesRead = 0;
Debug.Assert(stream.CanRead);
while (bytesRead < sizeBuffer.Length)
bytesRead += stream.Read(sizeBuffer, bytesRead, sizeBuffer.Length - bytesRead);
// Create a buffer for serialized data
var serializationLength = BitConverter.ToInt32(sizeBuffer);
var serializedDataBuffer = new byte[serializationLength];
// Get data from the stream
bytesRead = 0;
while (bytesRead < serializationLength)
bytesRead += stream.Read(serializedDataBuffer, bytesRead, serializationLength - bytesRead);
// Deserialize data into an object
var json = Encoding.UTF8.GetString(serializedDataBuffer);
// Deserialize the wrapped type correctly using reflection
var deserializedObject = JsonSerializer.Deserialize<T>(json);
if (deserializedObject is NetworkTransmittedUpdate {UpdateObject: { }} dynamicUpdateWrapper)
{
// In this block, we know we are wrapping data. The deserializer doesn't choose the write type by default, so we need to create a new
var innerData = dynamicUpdateWrapper.UpdateObject!.ToString();
var innerDataType = Type.GetType(dynamicUpdateWrapper.UpdateObjectType);
return new NetworkTransmittedUpdate
{
UpdateType = dynamicUpdateWrapper.UpdateType,
UpdateObjectType = dynamicUpdateWrapper.UpdateObjectType,
UpdateObject = JsonSerializer.Deserialize(innerData ?? string.Empty, innerDataType!)
} as T;
}
return deserializedObject;
}
/// <summary>
/// Serializes and writes an object to a stream
/// </summary>
/// <param name="stream">The stream to write UTF-8 data to</param>
/// <param name="value">An object to serialize and write</param>
/// <typeparam name="T">A serializable type</typeparam>
public static void WriteObject<T>(this Stream stream, T value)
{
var json = JsonSerializer.Serialize(value);
var bytes = Encoding.UTF8.GetBytes(json);
// Always send a number of bytes ahead, so the other side knows how much to read
stream.Write(BitConverter.GetBytes(bytes.Length));
// Send serialized data
stream.Write(bytes);
stream.Flush();
}
}
For some reason, the below test gets stuck while reading the length of object being sent.
[Fact]
public void TestChatMessageNetworkPackets()
{
// Setup
var listener = new TcpListener(IPAddress.Any, 12321);
listener.Start();
using var client = new TcpClient("localhost", 12321);
using var server = listener.AcceptTcpClient();
using var clientStream = client.GetStream();
using var serverStream = server.GetStream();
// Send and receive chat message
clientStream.WriteObject(new NetworkTransmittedUpdate()
{
UpdateObject = new string("Test message"),
UpdateType = UpdateType.ChatMessage,
UpdateObjectType = typeof(string).FullName!
});
var update = clientStream.ReadObject<NetworkTransmittedUpdate>();
}

Change this:
var update = clientStream.ReadObject<NetworkTransmittedUpdate>();
To this:
var update = serverStream.ReadObject<NetworkTransmittedUpdate>();
You want to write on the Client stream, then read on the Server stream since that's on the other side of the fence.

FCM notification from web api c# to android

I'm developing API via c# that will send notification to specific user ( android user) , then when user open the notification I want to redirect him to specific activity.
So I needed to send data along with notification message. I've tested it using Firebase Console and it's working fine , The notification is received and my launcher activity receive the extra from data has been sent
I've also tested it from my backend and the notification is received except that my launcher intent doesn't receive any extra.
I've been struggling for hours now , Any idea would help !
this is my code from c#
public String getNotification ()
{
string serverKey = "xxxx";
var result = "-1";
try
{
var webAddr = "https://fcm.googleapis.com/fcm/send";
var regID = "xxxx";
var httpWebRequest = (HttpWebRequest)WebRequest.Create(webAddr);
httpWebRequest.ContentType = "application/json";
httpWebRequest.Headers.Add("Authorization:key=" + serverKey);
httpWebRequest.Method = "POST";
using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream()))
{
string json = "{\"to\": \"" + regID +
"\",\"notification\": {\"title\": \"Testing\",\"body\": \"Hi Testing\"}" +
"," + "\"data:\"" + "{\"mymsg\":" + "\"h\" }}";
streamWriter.Write(json);
streamWriter.Flush();
}
var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();
using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
{
result = streamReader.ReadToEnd();
}
return result;
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
return "Can't Send";
}
}
}
And this is my launcher activity :
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.d("test" , "in main");
if (getIntent().getStringExtra("mymsg") != null) {
Log.d("test" , "has extra");
Intent intent = new Intent(this, Main2Activity.class);
startActivity(intent);
finish();
} else {
Log.d("test" , "no extra");
}

It looks like you have the wrong JSON:
," + "\"data:\"" + "{\"mymsg\":" + "\"h\" }} will be:
"data:" {
"mymsg":"h"
}
just correct your JSON. But I recommend using c# classes and serialization. Look at this simple example:
var payload = new {
to = "XXXX",
notification = new
{
body = "Test",
title = "Test"
},
data = new {
mymsg = "h"
}
}
// Using Newtonsoft.Json
string postbody = JsonConvert.SerializeObject(payload).ToString();
But its just example. You should create classes instead of anonym objects and using JsonProperty or another way to serialize the object. Something like that:
/// <summary>
/// Data for sending push-messages.
/// </summary>
public class PushData
{
/// <summary>
/// [IOS] Displaying message
/// </summary>
[JsonProperty("alert")]
public Alert Alert { get; set; }
/// <summary>
/// [IOS] badge value (can accept string representaion of number or "Increment")
/// </summary>
[JsonProperty("badge")]
public Int32? Badge { get; set; }
/// <summary>
/// [IOS] The name of sound to play
/// </summary>
[JsonProperty("sound")]
public String Sound { get; set; }
/// <summary>
/// [IOS>=7] Content to download in background
/// </summary>
/// <remarks>
/// Set 1 for silent mode
/// </remarks>
[JsonProperty("content-available")]
public Int32? ContentAvailable { get; set; }
/// <summary>
/// [IOS>=8] Category of interactive push with additional actions
/// </summary>
[JsonProperty("category")]
public String Category { get; set; }
/// <summary>
/// [Android] Used for collapsing some messages with same collapse_key
/// </summary>
[JsonProperty(PropertyName = "collapse_key")]
public String CollapseKey { get; set; }
/// <summary>
/// [Android] This parameter specifies how long (in seconds) the message should be kept in GCM storage if the device is offline.
/// The maximum time to live supported is 4 weeks, and the default value is 4 weeks.
/// </summary>
/// <value>
/// Time_to_live value of 0 means messages that can't be delivered immediately will be discarded
/// </value>
[JsonProperty("time_to_live")]
public Int32 TimeToLive { get; set; }
/// <summary>
/// [Android] Uri of activity to open when push activated by user
/// </summary>
[JsonProperty("url")]
public String Url { get; set; }
/// <summary>
/// Payload for push
/// </summary>
[JsonProperty("data")]
public Payload Payload { get; set; }
}
with message builder which serialize your message body to correct json string.

'RestClient' does not contain a definition for 'JsonSerializer' and no extension method 'JsonSerializer'

As i read readme.txt for latest RestSharp:
*** IMPORTANT CHANGE IN RESTSHARP VERSION 103 ***
In 103.0, JSON.NET was removed as a dependency.
If this is still installed in your project and no other libraries depend on
it you may remove it from your installed packages.
There is one breaking change: the default Json*Serializer* is no longer
compatible with Json.NET. To use Json.NET for serialization, copy the code
from https://github.com/restsharp/RestSharp/blob/86b31f9adf049d7fb821de8279154f41a17b36f7/RestSharp/Serializers/JsonSerializer.cs
and register it with your client:
var client = new RestClient();
client.JsonSerializer = new YourCustomSerializer();
The default Json*Deserializer* is mostly compatible, but it does not support
all features which Json.NET has (like the ability to support a custom [JsonConverter]
by decorating a certain property with an attribute). If you need these features, you
must take care of the deserialization yourself to get it working.
Im already installed Newtonsoft.Json with nu package manager, and im trying to register Json.NET to client variable, but didn't work. here is my code:
private void Form1_Load(object sender, EventArgs e)
{
var client = new RestClient("http://homestead.app/vendor");
client.JsonSerializer = new JsonSerializer(); <-- HERE IS THE ERROR
var request = new RestRequest("", Method.GET);
IRestResponse response = client.Execute(request);
var content = response.Content; // raw content as string
textBox1.Text = content;
}
the client.JsonSerializer property is not available.
Please kindly help me. thanks

The serializers for RestSharp must implement two interfaces:
RestSharp.Serializers.ISerializer
RestSharp.Serializers.IDeserializer
You must wrap the serializer from Newtonsoft to type with these interfaces.
There is working code from one project I worked on:
/// <summary>
/// Default JSON serializer for request bodies
/// Doesn't currently use the SerializeAs attribute, defers to Newtonsoft's attributes
/// </summary>
/// <remarks>
/// Based on http://blog.patrickmriley.net/2014/02/restsharp-using-jsonnet-serializer.html
/// </remarks>
public class RestSharpJsonNetSerializer : RestSharp.Serializers.ISerializer, RestSharp.Deserializers.IDeserializer
{
private readonly JsonSerializer serializer;
/// <summary>
/// Default serializer
/// </summary>
public RestSharpJsonNetSerializer()
{
this.ContentType = "application/json";
this.serializer = new JsonSerializer
{
MissingMemberHandling = MissingMemberHandling.Ignore,
NullValueHandling = NullValueHandling.Include,
DefaultValueHandling = DefaultValueHandling.Include
};
}
/// <summary>
/// Default serializer with overload for allowing custom Json.NET settings
/// </summary>
public RestSharpJsonNetSerializer(JsonSerializer serializer)
{
this.ContentType = "application/json";
this.serializer = serializer;
}
/// <summary>
/// Unused for JSON Serialization
/// </summary>
public string DateFormat { get; set; }
/// <summary>
/// Unused for JSON Serialization
/// </summary>
public string RootElement { get; set; }
/// <summary>
/// Unused for JSON Serialization
/// </summary>
public string Namespace { get; set; }
/// <summary>
/// Content type for serialized content
/// </summary>
public string ContentType { get; set; }
/// <summary>
/// Serialize the object as JSON
/// </summary>
/// <param name="obj">Object to serialize></param>
/// <returns>JSON as String</returns>
public string Serialize(object obj)
{
using (var stringWriter = new StringWriter())
{
using (var jsonTextWriter = new JsonTextWriter(stringWriter))
{
jsonTextWriter.Formatting = Formatting.Indented;
jsonTextWriter.QuoteChar = '"';
this.serializer.Serialize(jsonTextWriter, obj);
var result = stringWriter.ToString();
return result;
}
}
}
public T Deserialize<T>(RestSharp.IRestResponse response)
{
using (var strReader = new StringReader(response.Content))
{
using (var jsonReader = new JsonTextReader(strReader))
{
var data = this.serializer.Deserialize<T>(jsonReader);
return data;
}
}
}
}

The new readme.txt is updated at least in GitHub but the package still contains the old code.
So the answer of #TcKs is correct:
var request = new RestRequest();
request.JsonSerializer = new Shared.JsonSerializer();
var client = new RestClient();
client.Post(request);

It will be easy if you using mapper object when return
public YourResultBase Login(string username, string password)
{
var client = new RestClient("apiUrl");
var request = new RestRequest(Method.GET)
{
OnBeforeDeserialization = resp => { resp.ContentType = "application/json"; }
};
request.AddHeader("Cache-Control", "no-cache");
IRestResponse<YourResultBase> response = client.Execute<YourResultBase>(request);
var result = response.Data;
return result;
}

XML Serializing and Deserializing List Data in Android App

So I am trying to deserialize and serialize a List.
The issue: The list(list1) is not saving to the file called "ListData" which should be created if not already there, into the documents folder in the android internal storage.
I think the file may not be creating properly or something, or the filepath is incorrect. Below is how it should be functioning but that isn't working as explained with the issue above.
I want to save the filename as something like "ListData".
Also, needs to be saved into the Internal Storage somewhere such as the Data folder of the app or Documents in internal storage.
The following is what i have for the code, but I can't seem to find any help elsewhere to fix my issue. It doesn't work, any ideas for a solution to what I want it to do?
Code:
public abstract class DataHandler
{
public static void SaveLists()
{
string filePath = Android.OS.Environment.DirectoryDocuments;
string fileName = "ListData";
XmlSerializer serializer = new XmlSerializer(typeof(List<Item>));
Stream writer = new FileStream(filePath, FileMode.Create);
serializer.Serialize(writer, _LISTFROMANOTHERCLASS_);
writer.Close();
}
public static void LoadLists()
{
string filePath = Android.OS.Environment.DirectoryDocuments;
string fileName = "ListData";
XmlSerializer serializer = new XmlSerializer(typeof(List<Item>));
Stream reader = new FileStream(filePath, FileMode.Open);
List<Item> list1 = new List<Item>();
list1 = (List<Item>) serializer.Deserialize(reader);
_LISTFROMANOTHERCLASS_ = list1;
reader.Close();
}
}

Hi I have written a class to do these but with JSON serlization check is it helps it uses MVVM Cross, It has code written to encrypt and decrypt data you can avoid these parts
public class PersistantStorageHelper<T>
{
IMvxFileStoreAsync _mvxFileStoreAsync;
IMvxFileStore _mvxFileStore;
EDEngine bcEngine = new EDEngine(new AesEngine(), Encoding.UTF8);
string currentkey_temp_dev = "AthulHarikumar00";//This static key is not being used it is a just a place holder
public PersistantStorageHelper() {
this._mvxFileStore = Mvx.Resolve<IMvxFileStore>();
this._mvxFileStoreAsync = Mvx.Resolve<IMvxFileStoreAsync>();
bcEngine.SetPadding(new Pkcs7Padding());
currentkey_temp_dev = Constants.PassPhrase.Substring(4, 12)+"Road";
}
/// <summary>
///
/// </summary>
/// <param name="obj"></param>
/// <returns></returns>
public async Task<T> GetPersistantObject(T obj)
{
var fileName = (typeof(T).ToString().Replace(".", "_"));
var x= await GetPersistantObject(obj, fileName);
return x;
}
/// <summary>
/// If object exists returns the object else saves a plain object and returns it
/// </summary>
/// <param name="obj">empty placeholder object</param>
/// <returns>Filesystem object</returns>
public async Task<T> GetPersistantObject( T obj,string fileName) {
List<string> files = new List<string>(_mvxFileStore.GetFilesIn(_mvxFileStore.NativePath("")));
fileName = _mvxFileStore.NativePath(fileName);
if (!files.Contains(fileName))
{
var objJson = Newtonsoft.Json.JsonConvert.SerializeObject(obj);
objJson= bcEngine.Encrypt(objJson, currentkey_temp_dev);
await _mvxFileStoreAsync.WriteFileAsync(fileName,objJson);
}
else {
try
{
var temp = await _mvxFileStoreAsync.TryReadTextFileAsync(fileName);
var str = bcEngine.Decrypt(temp.Result, currentkey_temp_dev);
obj = Newtonsoft.Json.JsonConvert.DeserializeObject<T>(str);
}
catch(Exception e) {
var objJson = Newtonsoft.Json.JsonConvert.SerializeObject(obj);
objJson = bcEngine.Encrypt(objJson, currentkey_temp_dev);
await _mvxFileStoreAsync.WriteFileAsync(fileName, objJson);
}
}
return obj;
}
/// <summary>
///
/// </summary>
/// <param name="obj"></param>
/// <returns></returns>
public async Task<T> SetPersistantObject(T obj)
{
var fileName = _mvxFileStore.NativePath(typeof(T).ToString().Replace(".", "_"));
var temp = await SetPersistantObject(obj, fileName);
return temp;
}
/// <summary>
/// Saves object to persistant storage with encryption
/// </summary>
/// <param name="obj">object to be stored</param>
/// <returns>Saved object</returns>
public async Task<T> SetPersistantObject(T obj,string fileName)
{
List<string> files = new List<string>(_mvxFileStore.GetFilesIn(_mvxFileStore.NativePath("")));
fileName = _mvxFileStore.NativePath(fileName);
var objJson = Newtonsoft.Json.JsonConvert.SerializeObject(obj);
objJson = bcEngine.Encrypt(objJson, currentkey_temp_dev);
await _mvxFileStoreAsync.WriteFileAsync(fileName, objJson);
return obj;
}
}

java.util.List is not serializable, but java.util.ArrayList is. So just change List to ArrayList on both sites (left before variablename and right for constructor). Also check if your Item implements Serializable

Problem dynamically adding XML items to listbox, C#?

I'm pulling feeds for my RSS project and I am running into a problem of not knowing how to allow the user to load more items into the collection. At the current moment, everything loads at once. While this is in some cases all right, I would like the user to be able to choose how things get loaded in case they have a slow mobile connection.
This is borrowed code and thus it only adds to my confusion.
Where could i be able to inject code into this sample to allow a dynamic loading of items, say, 30 at a time?
Rss Class:
namespace MyRSSService
{
public class RssService
{
/// Gets the RSS items.
/// <param name="rssFeed">The RSS feed.</param>
/// <param name="onGetRssItemsCompleted">The on get RSS items completed.</param>
/// <param name="onError">The on error.</param>
public static void GetRssItems(string rssFeed, Action<IList<RssItem>> onGetRssItemsCompleted = null, Action<Exception> onError = null, Action onFinally = null)
{
WebClient webClient = new WebClient();
// register on download complete event
webClient.OpenReadCompleted += delegate(object sender, OpenReadCompletedEventArgs e)
{
try
{
// report error
if (e.Error != null)
{
if (onError != null)
{
onError(e.Error);
}
return;
}
// convert rss result to model
IList<RssItem> rssItems = new List<RssItem>();
Stream stream = e.Result;
XmlReader response = XmlReader.Create(stream);
{
SyndicationFeed feeds = SyndicationFeed.Load(response);
foreach (SyndicationItem f in feeds.Items)
{
RssItem rssItem = new RssItem(f.Title.Text, f.Summary.Text, f.PublishDate.ToString(), f.Links[0].Uri.AbsoluteUri);
rssItems.Add(rssItem);
}
}
// notify completed callback
if (onGetRssItemsCompleted != null)
{
onGetRssItemsCompleted(rssItems);
}
}
finally
{
// notify finally callback
if (onFinally != null)
{
onFinally();
}
}
};
webClient.OpenReadAsync(new Uri(rssFeed));
}
}
}
items setting class:
namespace MyRSSService
{
public class RssItem
{
/// <summary>
/// Initializes a new instance of the <see cref="RssItem"/> class.
/// </summary>
/// <param name="title">The title.</param>
/// <param name="summary">The summary.</param>
/// <param name="publishedDate">The published date.</param>
/// <param name="url">The URL.</param>
public RssItem(string title, string summary, string publishedDate, string url)
{
Title = title;
Summary = summary;
PublishedDate = publishedDate;
Url = url;
// Get plain text from html
PlainSummary = HttpUtility.HtmlDecode(Regex.Replace(summary, "<[^>]+?>", ""));
}
public string Title { get; set; }
public string Summary { get; set; }
public string PublishedDate { get; set; }
public string Url { get; set; }
public string PlainSummary { get; set; }
}
}
the binding C# to the page to display the feeds
public partial class FeedPage : PhoneApplicationPage
{
private const string WindowsPhoneBlogPosts = "http://feeds.bbci.co.uk/news/rss.xml";
public FeedPage()
{
InitializeComponent();
RssService.GetRssItems(WindowsPhoneBlogPosts, (items) => { listbox.ItemsSource = items; }, (exception) => { MessageBox.Show(exception.Message); }, null);
}
}

Unless the server where the feed is hosted provides an API to limit the number of returned items (for example, this practice is used for the Xbox Marketplace), you will be downloading the entire feed, even if you decide to only show a part of it.