I want to know about implementing a "push" chat server, which uses HTTP keepalive headers. I just came to know two technologies such chat servers use - long polling, and push - but I could not get any concepts regarding what happens behind the scenes.
Can anyone please help me ? Any client side / server side code would be appreciated a lot !!
Here is some comet code from the Tomcat Docs (hhttp://tomcat.apache.org/tomcat-7.0-doc/aio.html)
public class ChatServlet
extends HttpServlet implements CometProcessor {
protected ArrayList<HttpServletResponse> connections =
new ArrayList<HttpServletResponse>();
protected MessageSender messageSender = null;
public void init() throws ServletException {
messageSender = new MessageSender();
Thread messageSenderThread =
new Thread(messageSender, "MessageSender[" + getServletContext().getContextPath() + "]");
messageSenderThread.setDaemon(true);
messageSenderThread.start();
}
public void destroy() {
connections.clear();
messageSender.stop();
messageSender = null;
}
/**
* Process the given Comet event.
*
* #param event The Comet event that will be processed
* #throws IOException
* #throws ServletException
*/
public void event(CometEvent event)
throws IOException, ServletException {
HttpServletRequest request = event.getHttpServletRequest();
HttpServletResponse response = event.getHttpServletResponse();
if (event.getEventType() == CometEvent.EventType.BEGIN) {
log("Begin for session: " + request.getSession(true).getId());
PrintWriter writer = response.getWriter();
writer.println("<!doctype html public \"-//w3c//dtd html 4.0 transitional//en\">");
writer.println("<head><title>JSP Chat</title></head><body bgcolor=\"#FFFFFF\">");
writer.flush();
synchronized(connections) {
connections.add(response);
}
} else if (event.getEventType() == CometEvent.EventType.ERROR) {
log("Error for session: " + request.getSession(true).getId());
synchronized(connections) {
connections.remove(response);
}
event.close();
} else if (event.getEventType() == CometEvent.EventType.END) {
log("End for session: " + request.getSession(true).getId());
synchronized(connections) {
connections.remove(response);
}
PrintWriter writer = response.getWriter();
writer.println("</body></html>");
event.close();
} else if (event.getEventType() == CometEvent.EventType.READ) {
InputStream is = request.getInputStream();
byte[] buf = new byte[512];
do {
int n = is.read(buf); //can throw an IOException
if (n > 0) {
log("Read " + n + " bytes: " + new String(buf, 0, n)
+ " for session: " + request.getSession(true).getId());
} else if (n < 0) {
error(event, request, response);
return;
}
} while (is.available() > 0);
}
}
public class MessageSender implements Runnable {
protected boolean running = true;
protected ArrayList<String> messages = new ArrayList<String>();
public MessageSender() {
}
public void stop() {
running = false;
}
/**
* Add message for sending.
*/
public void send(String user, String message) {
synchronized (messages) {
messages.add("[" + user + "]: " + message);
messages.notify();
}
}
public void run() {
while (running) {
if (messages.size() == 0) {
try {
synchronized (messages) {
messages.wait();
}
} catch (InterruptedException e) {
// Ignore
}
}
synchronized (connections) {
String[] pendingMessages = null;
synchronized (messages) {
pendingMessages = messages.toArray(new String[0]);
messages.clear();
}
// Send any pending message on all the open connections
for (int i = 0; i < connections.size(); i++) {
try {
PrintWriter writer = connections.get(i).getWriter();
for (int j = 0; j < pendingMessages.length; j++) {
writer.println(pendingMessages[j] + "<br>");
}
writer.flush();
} catch (IOException e) {
log("IOExeption sending message", e);
}
}
}
}
}
}
}
There are many specific techniques, generally now known under the name Comet. The Wikipedia article linked there is a pretty good intro.
Also see The Long Polling Technique.
Related
We are using SignalR for information exchange.
When the web browser is connected a timer starts, but it is not stopping when user close the browser.
Here is the code. starttimer function runs when browser connected.
When user disconnect the browser, timer still running on the server.
[HubName("myChatHub")]
public class InboundCallsDataShare : Hub
{
private OverrideTimer timer ;
private List<GroupNConnectionId> groupsList = new List<GroupNConnectionId>();
public void send(string message)
{
Clients.All.addMessage(message);
//Clients..addMessage(message);
}
public void starttimer(string queue)
{
//var connectionId = this.Context.ConnectionId;
//GroupNConnectionId objGroupNConnectionId=new GroupNConnectionId();
//objGroupNConnectionId.Group = queue;
//objGroupNConnectionId.ConnectionID = connectionId;
//if(groupsList.Contains(objGroupNConnectionId))return;
//////////////////////////////////////////////////////
//groupsList.Add(objGroupNConnectionId);
Groups.Add(this.Context.ConnectionId, queue);
timer = new OverrideTimer(queue);
timer.Interval = 15000;
timer.Elapsed +=new EventHandler<BtElapsedEventArgs>(timer_Elapsed);
//first time call
timer_Elapsed(timer,new BtElapsedEventArgs(){Queue = queue});
//ends
timer.Start();
Console.WriteLine("Timer for queue " +queue);
}
public override Task OnConnected()
{
return base.OnConnected();
}
public override Task OnDisconnected()
{
//timer.Stop();
return base.OnDisconnected();
}
public void getdatafromxml(string queue)
{
string list = (new Random()).Next(1, 10000).ToString();
Clients.All.getList(list);
//Clients..addMessage(message);
}
public ICBMObject GetInterationList(string queue)
{
//ININInterations.QueueListViewItemData _obj = new ININInterations.QueueListViewItemData();
return GetInboundCallCountFromXML(queue);
//return _obj.MainFunctionIB();
}
void timer_Elapsed(object sender, BtElapsedEventArgs e)
{
ICBMObject objICBMObject = GetInboundCallCountFromXML(e.Queue);
Clients.Group(e.Queue).getList(objICBMObject);
CreateFile(e.Queue);
//Clients.All.getList(objICBMObject);
}
private void CreateFile(string queue)
{
string path = #"D:\t.txt";
string text = File.ReadAllText(path);
text += queue+ DateTime.Now.ToString() + Environment.NewLine;
File.WriteAllText(path, text);
}
public ICBMObject GetInboundCallCountFromXML(string queue)
{
FileStream fs = null;
int totalInboundCalls = 0,
totalInboundCallsUnassigned = 0;
string longestDuration = "";
bool updateText = false;
try
{
XmlDataDocument xmldoc = new XmlDataDocument();
XmlNodeList xmlnode;
int i = 0;
string str = null;
fs = new FileStream(AppDomain.CurrentDomain.BaseDirectory + "InboundXML/" + queue + ".xml",
FileMode.Open, FileAccess.Read);
if (fs.CanRead)
{
xmldoc.Load(fs);
xmlnode = xmldoc.GetElementsByTagName(queue);
for (i = 0; i <= xmlnode.Count - 1; i++)
{
totalInboundCalls = Convert.ToInt32(xmlnode[i].ChildNodes.Item(0).InnerText.Trim());
totalInboundCallsUnassigned = Convert.ToInt32(xmlnode[i].ChildNodes.Item(1).InnerText.Trim());
longestDuration = xmlnode[i].ChildNodes.Item(2).InnerText.Trim();
}
updateText = true;
}
}
catch (Exception)
{
}
finally
{
if (fs != null)
{
fs.Close();
fs.Dispose();
}
}
return new ICBMObject()
{
TotalInboundCalls = totalInboundCalls,
TotalInboundCallsUnassigned = totalInboundCallsUnassigned,
LongestDuration = longestDuration,
UpdateText = updateText
//string.Format("{0:D2}:{1:D2}:{2:D2}",
// _LongetInbound.Hours,
// _LongetInbound.Minutes,
// _LongetInbound.Seconds)
};
}
}
Besides the fact that its commented out? Did you put a break point on the timer to see if its getting hit at all? It might be that there is a delay in calling the onDisconnect, if the timeout property is set too large, it might not fire. it might be entering onReconnected if it does not know the client is closed.
I have a form, 2 buttons , 1 textbox. Button 1 processes the TaskException_click.
What I wanted to do is understanding the async task/void difference. But checking multiple examples I still do not understand or get it to work. Below my code.
When I click the taskexception button, the unobservedtaskexception is not executed (I expected that).
When I click it another time, the event is executed with the exception of the first click. However the UI is not updated (actually it hangs). Would like to know what I am doing wrong.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace test
{
public partial class main : Form
{
public main()
{
InitializeComponent();
TaskScheduler.UnobservedTaskException += TaskScheduler_UnobservedTaskException;
}
void TaskScheduler_UnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs e)
{
//textBox1.Text = "Unobserved Exception caught ";
e.SetObserved();
if (this.InvokeRequired)
{
this.Invoke((MethodInvoker)delegate()
{
//codes to do whatever i wan to do with the GUI
//Examples of it would be disposing a flowlayout panel
//and re-adding it back and populating it again to
//show the refreshed values.
textBox1.Text = "Unobserved Exception caught " + e.Exception.Message;
});
}
else
{
textBox1.Text = "Unobserved Exception caught " + e.Exception.Message;
}
}
private int i = 0;
// Add async here! You can always add these to events
private async void TaskException_Click(object sender, EventArgs e)
{
textBox1.Text = "";
try
{
Task t = TaskThrowAnException();
textBox1.Text = "done";
t = null;
Thread.Sleep(100);
GC.Collect();
GC.WaitForPendingFinalizers();
GC.Collect();
}
catch (Exception ex)
{
textBox1.Text = "Exception caught";
}
}
private async Task TaskThrowAnException()
{
//await Task.Delay(1000);
i++;
throw new Exception("Task" + i.ToString());
}
private async void VoidException_Click(object sender, EventArgs e)
{
textBox1.Text = "";
try
{
VoidThrowAnException();
textBox1.Text = "done";
}
catch (Exception ex )
{
textBox1.Text = "Exception caught";
}
}
private async void VoidThrowAnException()
{
//await Task.Delay(1000);
throw new Exception("Void");
}
}
}
For the TaskException case the exception is stored in the Task this is the expected behavior for async methods returning Task. If you want the exception to be thrown you need to observe the exception by awaiting the Task or calling Result or Wait() on the Task.
If the exception is unobserved it should get thrown when the Task is finalized, the only thing I can conclude is that somehow the task is not being finalized when you call
Thread.Sleep(100);
GC.Collect();
GC.WaitForPendingFinalizers();
GC.Collect();
I am nor sure why the local variable is not GCed, if add another button and you put the code above in the button handler (e.g Clear_Click) everything works as expected. I thought the generated code must somehow have a link to the task variable but I couldn't find any link.
Here is the generated code from Reflector:
namespace WindowsFormsApplication1
{
using System;
using System.ComponentModel;
using System.Diagnostics;
using System.Drawing;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
public class Form1 : Form
{
private IContainer components = null;
private int i = 0;
private Button TaskException;
private TextBox textBox1;
private Button VoidException;
public Form1()
{
this.InitializeComponent();
TaskScheduler.UnobservedTaskException += new EventHandler<UnobservedTaskExceptionEventArgs>(this.TaskScheduler_UnobservedTaskException);
}
protected override void Dispose(bool disposing)
{
if (disposing && (this.components != null))
{
this.components.Dispose();
}
base.Dispose(disposing);
}
private void InitializeComponent()
{
this.textBox1 = new TextBox();
this.TaskException = new Button();
this.VoidException = new Button();
base.SuspendLayout();
this.textBox1.Location = new Point(13, 13);
this.textBox1.Multiline = true;
this.textBox1.Name = "textBox1";
this.textBox1.Size = new Size(0x20d, 0x13f);
this.textBox1.TabIndex = 0;
this.TaskException.Location = new Point(13, 0x16d);
this.TaskException.Name = "TaskException";
this.TaskException.Size = new Size(0x9b, 0x17);
this.TaskException.TabIndex = 1;
this.TaskException.Text = "TaskException";
this.TaskException.UseVisualStyleBackColor = true;
this.TaskException.Click += new EventHandler(this.TaskException_Click);
this.VoidException.Location = new Point(0xda, 0x16d);
this.VoidException.Name = "VoidException";
this.VoidException.Size = new Size(0xab, 0x17);
this.VoidException.TabIndex = 2;
this.VoidException.Text = "VoidException";
this.VoidException.UseVisualStyleBackColor = true;
this.VoidException.Click += new EventHandler(this.VoidException_Click);
base.AutoScaleDimensions = new SizeF(6f, 13f);
base.AutoScaleMode = AutoScaleMode.Font;
base.ClientSize = new Size(550, 430);
base.Controls.Add(this.VoidException);
base.Controls.Add(this.TaskException);
base.Controls.Add(this.textBox1);
base.Name = "Form1";
this.Text = "Form1";
base.ResumeLayout(false);
base.PerformLayout();
}
[DebuggerStepThrough, AsyncStateMachine(typeof(<TaskException_Click>d__4))]
private void TaskException_Click(object sender, EventArgs e)
{
<TaskException_Click>d__4 d__;
d__.<>4__this = this;
d__.sender = sender;
d__.e = e;
d__.<>t__builder = AsyncVoidMethodBuilder.Create();
d__.<>1__state = -1;
d__.<>t__builder.Start<<TaskException_Click>d__4>(ref d__);
}
private void TaskScheduler_UnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs e)
{
MethodInvoker method = null;
e.SetObserved();
if (base.InvokeRequired)
{
if (method == null)
{
method = (MethodInvoker) (() => (this.textBox1.Text = "Unobserved Exception caught " + e.Exception.Message));
}
base.BeginInvoke(method);
}
else
{
this.textBox1.Text = "Unobserved Exception caught " + e.Exception.Message;
}
}
[AsyncStateMachine(typeof(<TaskThrowAnException>d__6)), DebuggerStepThrough]
private Task TaskThrowAnException()
{
<TaskThrowAnException>d__6 d__;
d__.<>4__this = this;
d__.<>t__builder = AsyncTaskMethodBuilder.Create();
d__.<>1__state = -1;
d__.<>t__builder.Start<<TaskThrowAnException>d__6>(ref d__);
return d__.<>t__builder.Task;
}
[DebuggerStepThrough, AsyncStateMachine(typeof(<VoidException_Click>d__8))]
private void VoidException_Click(object sender, EventArgs e)
{
<VoidException_Click>d__8 d__;
d__.<>4__this = this;
d__.sender = sender;
d__.e = e;
d__.<>t__builder = AsyncVoidMethodBuilder.Create();
d__.<>1__state = -1;
d__.<>t__builder.Start<<VoidException_Click>d__8>(ref d__);
}
[AsyncStateMachine(typeof(<VoidThrowAnException>d__a)), DebuggerStepThrough]
private void VoidThrowAnException()
{
<VoidThrowAnException>d__a _a;
_a.<>4__this = this;
_a.<>t__builder = AsyncVoidMethodBuilder.Create();
_a.<>1__state = -1;
_a.<>t__builder.Start<<VoidThrowAnException>d__a>(ref _a);
}
[CompilerGenerated]
private struct <TaskException_Click>d__4 : IAsyncStateMachine
{
public int <>1__state;
public Form1 <>4__this;
public AsyncVoidMethodBuilder <>t__builder;
public EventArgs e;
public object sender;
private void MoveNext()
{
try
{
if (this.<>1__state != -3)
{
this.<>4__this.textBox1.Text = "";
try
{
Task task = this.<>4__this.TaskThrowAnException();
this.<>4__this.textBox1.Text = "done";
task = null;
}
catch (Exception)
{
this.<>4__this.textBox1.Text = "Exception caught";
}
Thread.Sleep(100);
GC.Collect();
GC.WaitForPendingFinalizers();
GC.Collect();
}
}
catch (Exception exception2)
{
this.<>1__state = -2;
this.<>t__builder.SetException(exception2);
return;
}
this.<>1__state = -2;
this.<>t__builder.SetResult();
}
[DebuggerHidden]
private void SetStateMachine(IAsyncStateMachine param0)
{
this.<>t__builder.SetStateMachine(param0);
}
}
[CompilerGenerated]
private struct <TaskThrowAnException>d__6 : IAsyncStateMachine
{
public int <>1__state;
public Form1 <>4__this;
public AsyncTaskMethodBuilder <>t__builder;
private void MoveNext()
{
try
{
if (this.<>1__state != -3)
{
this.<>4__this.i++;
throw new Exception("Task" + this.<>4__this.i.ToString());
}
}
catch (Exception exception)
{
this.<>1__state = -2;
this.<>t__builder.SetException(exception);
return;
}
this.<>1__state = -2;
this.<>t__builder.SetResult();
}
[DebuggerHidden]
private void SetStateMachine(IAsyncStateMachine param0)
{
this.<>t__builder.SetStateMachine(param0);
}
}
[CompilerGenerated]
private struct <VoidException_Click>d__8 : IAsyncStateMachine
{
public int <>1__state;
public Form1 <>4__this;
public AsyncVoidMethodBuilder <>t__builder;
public EventArgs e;
public object sender;
private void MoveNext()
{
try
{
if (this.<>1__state != -3)
{
this.<>4__this.textBox1.Text = "";
try
{
this.<>4__this.VoidThrowAnException();
this.<>4__this.textBox1.Text = "done";
}
catch (Exception)
{
this.<>4__this.textBox1.Text = "Exception caught";
}
}
}
catch (Exception exception2)
{
this.<>1__state = -2;
this.<>t__builder.SetException(exception2);
return;
}
this.<>1__state = -2;
this.<>t__builder.SetResult();
}
[DebuggerHidden]
private void SetStateMachine(IAsyncStateMachine param0)
{
this.<>t__builder.SetStateMachine(param0);
}
}
[CompilerGenerated]
private struct <VoidThrowAnException>d__a : IAsyncStateMachine
{
public int <>1__state;
public Form1 <>4__this;
public AsyncVoidMethodBuilder <>t__builder;
private void MoveNext()
{
try
{
if (this.<>1__state != -3)
{
SynchronizationContext current = SynchronizationContext.Current;
throw new Exception("Void");
}
}
catch (Exception exception)
{
this.<>1__state = -2;
this.<>t__builder.SetException(exception);
return;
}
this.<>1__state = -2;
this.<>t__builder.SetResult();
}
[DebuggerHidden]
private void SetStateMachine(IAsyncStateMachine param0)
{
this.<>t__builder.SetStateMachine(param0);
}
}
}
}
Scenario - upload binary data in the body of a post, handle a response body containing JSON.
How to do the following using Volley?
curl -X POST -H "X-Application-Id: 3KxPB" -H "X-REST-API-Key: jkuI9" -H "Content-Type: audio/3gp" --data-binary '#test.3gp' https://host/1/files/audio
IMO - there is a gap in Volley handling binary POST body types that apache httpclient handles in subclasses of abstracthttpentity. If buffered binary data generated on the phone by camera, microphone, or other binary output sensors needs a mechanism to be wrapped and written to the body of a POST how to do it in volley?
I've looked at PoolingByteArrayOutputStream and would like to do something like fill the buffer and get the PBAOutStrm ,writing to PBAOutStrm from the buffer and then flipping OutStrm to InputStream and then wrap it in the body of a POST request as something like a ByteArrayEntity. I cant see how to do that in volley.
To send binary data you can do something like what I did in this answer How to send a “multipart/form-data” POST in Android with Volley .
I was able to solve this using a Volley GsonRequest:
public class MainActivity extends AppCompatActivity {
String url = "https://arcane-anchorage-34204.herokuapp.com/handleCode";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
JSONObject jsonBody = null;
try {
jsonBody = new JSONObject ("{\"code\":\"NZ4UBUB\"}");
} catch (JSONException e) {
Toast.makeText(getApplicationContext(), "Error e = " + e, Toast.LENGTH_SHORT).show();
}
Map<String, String> headers = new HashMap<String, String>();
headers.put("Content-Type", "application/json");
RequestQueue queue = Volley.newRequestQueue(this);
GsonRequest<Routine[]> gsonRequest = new GsonRequest<Routine[]>(Request.Method.POST, url, Routine[].class, headers, new Response.Listener<Routine[]>() {
#Override
public void onResponse(Routine[] routineData) {
TextView serverData = (TextView)findViewById(R.id.serverData);
String complete = "";
String repeat = "";
String hold = "";
String perform = "";
String txtData = "";
for (int i = 0; i < routineData.length; i++) {
complete = (routineData[i].instructions.complete != null) ? "Complete: " + routineData[i].instructions.complete : "";
repeat = (routineData[i].instructions.repeat != null) ? "Repeat: " + routineData[i].instructions.repeat : "";
hold = (routineData[i].instructions.hold != null) ? "Hold: " + routineData[i].instructions.hold : "";
perform = (routineData[i].instructions.perform != null) ? "Perform: " + routineData[i].instructions.perform : "";
txtData += "DESCRIPTION: " + routineData[i].description[0] + ": " + routineData[i].description[1] + ", " + complete + ", " + repeat + ", " + hold + ", " + perform + " ";
}
serverData.setText("Response: " + txtData);
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError volleyError) {
TextView serverData = (TextView)findViewById(R.id.serverData);
serverData.setText("Response: " + volleyError.toString());
}
}, jsonBody);
queue.add(gsonRequest);
}
public class GsonRequest<T> extends Request<T> {
private final Gson gson = new Gson();
private final Class<T> clazz;
private final Map<String, String> headers;
private final Response.Listener<T> listener;
private JSONObject parameters = null;
/**
* Make a GET request and return a parsed object from JSON.
*
* #param url URL of the request to make
* #param clazz Relevant class object, for Gson's reflection
* #param headers Map of request headers
*/
public GsonRequest(int method, String url, Class<T> clazz, Map<String, String> headers,
Response.Listener<T> listener, Response.ErrorListener errorListener) {
super(method, url, errorListener);
this.clazz = clazz;
this.headers = headers;
this.listener = listener;
}
public GsonRequest(int method, String url, Class<T> clazz, Map<String, String> headers,
Response.Listener<T> listener, Response.ErrorListener errorListener, JSONObject parameters) {
this(method, url, clazz, headers, listener, errorListener);
this.parameters = parameters;
}
#Override
public Map<String, String> getHeaders() throws AuthFailureError {
return headers != null ? headers : super.getHeaders();
}
#Override
public String getBodyContentType() {
return "application/json";
}
#Override
public byte[] getBody() throws AuthFailureError {
try {
return parameters.toString().getBytes(getParamsEncoding());
} catch (UnsupportedEncodingException e) {
}
return null;
}
#Override
protected void deliverResponse(T response) {
listener.onResponse(response);
}
#Override
protected Response<T> parseNetworkResponse(NetworkResponse response) {
try {
String json = new String(
response.data, HttpHeaderParser.parseCharset(response.headers));
Log.i("RESPONSE", json);
return Response.success(
gson.fromJson(json, clazz), HttpHeaderParser.parseCacheHeaders(response));
} catch (UnsupportedEncodingException e) {
return Response.error(new ParseError(e));
} catch (JsonSyntaxException e) {
return Response.error(new ParseError(e));
}
}
}
}
I need a way to save and load the Page State in a persistent manner (Session). The Project i need this for is an Intranet Web Application which has several Configuration Pages and some of them need a Confirmation if they are about to be saved. The Confirmation Page has to be a seperate Page. The use of JavaScript is not possible due to limitations i am bound to. This is what i could come up with so far:
ConfirmationRequest:
[Serializable]
public class ConfirmationRequest
{
private Uri _url;
public Uri Url
{ get { return _url; } }
private byte[] _data;
public byte[] Data
{ get { return _data; } }
public ConfirmationRequest(Uri url, byte[] data)
{
_url = url;
_data = data;
}
}
ConfirmationResponse:
[Serializable]
public class ConfirmationResponse
{
private ConfirmationRequest _request;
public ConfirmationRequest Request
{ get { return _request; } }
private ConfirmationResult _result = ConfirmationResult.None;
public ConfirmationResult Result
{ get { return _result; } }
public ConfirmationResponse(ConfirmationRequest request, ConfirmationResult result)
{
_request = request;
_result = result;
}
}
public enum ConfirmationResult { Denied = -1, None = 0, Granted = 1 }
Confirmation.aspx:
protected void Page_Load(object sender, EventArgs e)
{
if (Request.UrlReferrer != null)
{
string key = "Confirmation:" + Request.UrlReferrer.PathAndQuery;
if (Session[key] != null)
{
ConfirmationRequest confirmationRequest = Session[key] as ConfirmationRequest;
if (confirmationRequest != null)
{
Session[key] = new ConfirmationResponse(confirmationRequest, ConfirmationResult.Granted);
Response.Redirect(confirmationRequest.Url.PathAndQuery, false);
}
}
}
}
PageToConfirm.aspx:
private bool _confirmationRequired = false;
protected void btnSave_Click(object sender, EventArgs e)
{
_confirmationRequired = true;
Response.Redirect("Confirmation.aspx", false);
}
protected override void SavePageStateToPersistenceMedium(object state)
{
if (_confirmationRequired)
{
using (MemoryStream stream = new MemoryStream())
{
LosFormatter formatter = new LosFormatter();
formatter.Serialize(stream, state);
stream.Flush();
Session["Confirmation:" + Request.UrlReferrer.PathAndQuery] = new ConfirmationRequest(Request.UrlReferrer, stream.ToArray());
}
}
base.SavePageStateToPersistenceMedium(state);
}
I can't seem to find a way to load the Page State after being redirected from the Confirmation.aspx to the PageToConfirm.aspx, can anyone help me out on this one?
If you mean view state, try using Server.Transfer instead of Response.Redirect.
If you set the preserveForm parameter
to true, the target page will be able
to access the view state of the
previous page by using the
PreviousPage property.
use this code this works fine form me
public class BasePage
{
protected override PageStatePersister PageStatePersister
{
get
{
return new SessionPageStatePersister(this);
}
}
protected void Page_PreRender(object sender, EventArgs e)
{
//Save the last search and if there is no new search parameter
//Load the old viewstate
try
{ //Define name of the pages for u wanted to maintain page state.
List<string> pageList = new List<string> { "Page1", "Page2"
};
bool IsPageAvailbleInList = false;
foreach (string page in pageList)
{
if (this.Title.Equals(page))
{
IsPageAvailbleInList = true;
break;
}
}
if (!IsPostBack && Session[this + "State"] != null)
{
if (IsPageAvailbleInList)
{
NameValueCollection formValues = (NameValueCollection)Session[this + "State"];
String[] keysArray = formValues.AllKeys;
if (keysArray.Length > 0)
{
for (int i = 0; i < keysArray.Length; i++)
{
Control currentControl = new Control();
currentControl = Page.FindControl(keysArray[i]);
if (currentControl != null)
{
if (currentControl.GetType() == typeof(System.Web.UI.WebControls.TextBox))
((TextBox)currentControl).Text = formValues[keysArray[i]];
else if (currentControl.GetType() == typeof(System.Web.UI.WebControls.DropDownList))
((DropDownList)currentControl).SelectedValue = formValues[keysArray[i]].Trim();
else if (currentControl.GetType() == typeof(System.Web.UI.WebControls.CheckBox))
{
if (formValues[keysArray[i]].Equals("on"))
((CheckBox)currentControl).Checked = true;
}
}
}
}
}
}
if (Page.IsPostBack && IsPageAvailbleInList)
{
Session[this + "State"] = Request.Form;
}
}
catch (Exception ex)
{
LogHelper.PrintError(string.Format("Error occured while loading {0}", this), ex);
Master.ShowMessageBox(enMessageType.Error, ErrorMessage.GENERIC_MESSAGE);
}
}
}
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I understand that there are already alot of web server out there.
But i feel like creating one for learning purpose.
Is it something i should try to figure out and any guides or tutorials on this?
In java:
Create a ServerSocket and have this continually listen for connections - when a connection request comes in handle it by by parsing the HTTP request header, get the resource indicated and add some header information before sending back to the client. eg.
public class Server implements Runnable {
protected volatile boolean keepProcessing = true;
protected ServerSocket serverSocket;
protected static final int DEFAULT_TIMEOUT = 100000;
protected ExecutorService executor = Executors.newCachedThreadPool();
public Server(int port) throws IOException {
serverSocket = new ServerSocket(port);
serverSocket.setSoTimeout(DEFAULT_TIMEOUT);
}
#Override
public void run() {
while (keepProcessing) {
try {
Socket socket = serverSocket.accept();
System.out.println("client accepted");
executor.execute(new HttpRequest(socket));
} catch (Exception e) {
}
}
closeIgnoringException(serverSocket);
}
protected void closeIgnoringException(ServerSocket serverSocket) {
if (serverSocket != null) {
try {
serverSocket.close();
} catch (IOException ignore) {
}
}
}
public static void main(String[] args) {
ExecutorService executor = Executors.newCachedThreadPool();
try {
executor.execute(new WebServer(6789));
} catch (Exception e) {
e.printStackTrace();
}
}
}
final class HttpRequest implements Runnable {
final static String CRLF = "\r\n";
private Socket socket;
public HttpRequest(Socket socket) {
this.socket = socket;
}
public void run() {
try {
processRequest();
} catch (Exception e) {
System.out.println(e);
}
}
private void processRequest() throws Exception {
DataOutputStream os = new DataOutputStream(socket.getOutputStream());
BufferedReader br = new BufferedReader(new InputStreamReader(socket
.getInputStream()));
String requestLine = br.readLine();
System.out.println();
System.out.println(requestLine);
List<String> tokens = Arrays.asList(requestLine.split(" "));
Iterator<String> it = tokens.iterator();
it.next(); // skip over the method, which should be "GET"
String fileName = it.next();
fileName = "." + fileName;
FileInputStream fis = null;
boolean fileExists = true;
try {
fis = new FileInputStream(fileName);
} catch (FileNotFoundException e) {
fileExists = false;
}
String statusLine = null;
String contentTypeLine = null;
String entityBody = null;
String contentType = null;
if (fileExists) {
statusLine = "HTTP/1.0 200 OK";
contentType = contentType(fileName);
contentTypeLine = "Content-type: " + contentType + CRLF;
} else {
statusLine = "HTTP/1.0 404 NOT FOUND";
contentType = "text/html";
contentTypeLine = "Content-type: " + contentType + CRLF;
entityBody = "<HTML>" + "<HEAD><TITLE>Not Found</TITLE></HEAD>"
+ "<BODY>" + statusLine + " Not Found</BODY></HTML>";
}
os.writeBytes(statusLine);
os.writeBytes(contentTypeLine);
os.writeBytes(CRLF);
if (fileExists) {
sendBytes(fis, os);
fis.close();
} else {
os.writeBytes(entityBody);
}
String headerLine = null;
while ((headerLine = br.readLine()).length() != 0) {
System.out.println(headerLine);
}
os.close();
br.close();
socket.close();
}
private static void sendBytes(InputStream fis, DataOutputStream os)
throws Exception {
byte[] buffer = new byte[1024];
int bytes = 0;
while ((bytes = fis.read(buffer)) != -1) {
os.write(buffer, 0, bytes);
}
}
private static String contentType(String fileName) {
if (fileName.endsWith(".htm") || fileName.endsWith(".html")) {
return "text/html";
}
if (fileName.endsWith(".jpg") || fileName.endsWith(".jpeg")) {
return "image/jpeg";
}
if (fileName.endsWith(".gif")) {
return "image/gif";
}
if (fileName.endsWith(".txt")) {
return "text/plain";
}
if (fileName.endsWith(".pdf")) {
return "application/pdf";
}
return "application/octet-stream";
}
}
A Simple Webserver in C++ for Windows
Hope this helps you ; )
Alternatives
This project contains a modular web server in CodePlex
This article explains how to write a simple web server application using C# from CodeGuru
Start with understanding TCP/IP and the whole Internet protocol suite.
Then learn the HTTP 1.0 and 1.1 protocols.
That should start you on the way to understanding what you need to write in order to create a webserver from scratch.
Try asio from boost!
Boost.Asio is a cross-platform C++ library for network and low-level I/O programming that provides developers with a consistent asynchronous model using a modern C++ approach.
Most scripting language are capable and have plenty of examples on writing web servers. This route will give you a gentle introduction.