I'm trying to use an XPC Service for inter-process communication. I've added an XPC service target to my project, and then when I try doing a xpc_connection_send_message I get EXC_BAD_INSTRUCTION. As far as I can tell, I am correctly initializing and starting the connection.
serviceConnection = xpc_connection_create("com.foo.bar.MyService", dispatch_get_main_queue());
xpc_connection_set_event_handler(serviceConnection, ^(xpc_object_t event) {
xpc_type_t type = xpc_get_type(event);
if (type == XPC_TYPE_ERROR) {
if (event == XPC_ERROR_CONNECTION_INTERRUPTED) {
// The service has either cancaled itself, crashed, or been
// terminated. The XPC connection is still valid and sending a
// message to it will re-launch the service. If the service is
// state-full, this is the time to initialize the new service.
}
else if (event == XPC_ERROR_CONNECTION_INVALID) {
// The service is invalid. Either the service name supplied to
// xpc_connection_create() is incorrect or we (this process) have
// canceled the service; we can do any cleanup of appliation
// state at this point.
NSLog(#"Uh oh, connection invalid");
xpc_release(serviceConnection);
serviceConnection = nil;
//xpc_release(stack);
//stack = NULL;
}
else {
NSLog(#"Unknown XPC error.");
}
}
});
xpc_connection_resume(serviceConnection);
and then to send the message
xpc_object_t message = xpc_data_create(NULL, 0);
....
xpc_connection_send_message(serviceConnection, message);
Is there anything I'm missing here? Is it somehow failing to find and connect to the service?
Related
I have declared three different message types in OMNeT++:
Layer
Ack
Reject
What I want to achieve is that every node in my network can send any type of message mentioned above. So that every message type has its own variables. But since the handleMessage(cMessage*) function accepts cMessage* type, I need to know the type of message to be able to cast it accordingly.
How would I go about it?
Here is my Layer message type:
message Layer {
int layer;
simtime_t timeFrame;
}
Each your message type is represented by a class that inherits from cMessage. Therefore, dynamic_cast may be used to recognize the type of message, for example this way:
void YourClass::handleMessage(cMessage * msg) {
Layer * layer = dynamic_cast<Layer*> (msg);
if (layer != nullptr) {
// received Layer
} else {
Ack* ack = dynamic_cast<Ack*> (msg);
if (ack != nullptr) {
// received Ack
} else {
Reject* rej= dynamic_cast<Reject*> (msg);
if (rej != nullptr) {
// received Reject
}
}
}
I am unable to use cancellation tokens to stop a TCP Listener. The first code extract is an example where I can successfully stop a test while loop in a method from another class. So I don't understand why I cant apply this similar logic to the TCP Listener Class. Spent many days reading convoluted answers on this topic and cannot find a suitable solution.
My software application requires that the TCP Listener must give the user the ability to stop it from the server end, not the client. If a user wants to re-configure the port number for this listener then they would currently have to shutdown the software in order for Windows to close the underlying socket, this is no good as would affect the other services running in my app.
This first extract of code is just an example where I am able to stop a while loop from running, this works OK but is not that relevant other than the faat I would expect this to work for my TCP Listener:
public void Cancel(CancellationToken cancelToken) // EXAMPLE WHICH IS WORKING
{
Task.Run(async () =>
{
while (!cancelToken.IsCancellationRequested)
{
await Task.Delay(500);
log.Info("Test Message!");
}
}, cancelToken);
}
Now below is the actual TCP Listener code I am struggling with
public void TcpServerIN(string inboundEncodingType, string inboundIpAddress, string inboundLocalPortNumber, CancellationToken cancelToken)
{
TcpListener listener = null;
Task.Run(() =>
{
while (!cancelToken.IsCancellationRequested)
{
try
{
IPAddress localAddr = IPAddress.Parse(inboundIpAddress);
int port = int.Parse(inboundLocalPortNumber);
listener = new TcpListener(localAddr, port);
// Start listening for client requests.
listener.Start();
log.Info("TcpListenerIN listener started");
// Buffer for reading data
Byte[] bytes = new Byte[1024];
String data = null;
// Enter the listening loop.
while (true)
{
// Perform a blocking call to accept client requests.
TcpClient client = listener.AcceptTcpClient();
// Once each client has connected, start a new task with included parameters.
var task = Task.Run(() =>
{
// Get a stream object for reading and writing
NetworkStream stream = client.GetStream();
data = null;
int i;
// Loop to receive all the data sent by the client.
while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
{
// Select Encoding format set by string inboundEncodingType parameter.
if (inboundEncodingType == "UTF8") { data = Encoding.UTF8.GetString(bytes, 0, i); }
if (inboundEncodingType == "ASCII") { data = Encoding.ASCII.GetString(bytes, 0, i); }
// Use this if you want to echo each message directly back to TCP Client
//stream.Write(msg, 0, msg.Length);
// If any TCP Clients are connected then pass the appended string through
// the rules engine for processing, if not don't send.
if ((listConnectedClients != null) && (listConnectedClients.Any()))
{
// Pass the appended message string through the SSSCRulesEngine
SendMessageToAllClients(data);
}
}
// When the remote client disconnetcs, close/release the socket on the TCP Server.
client.Close();
});
}
}
catch (SocketException ex)
{
log.Error(ex);
}
finally
{
// If statement is required to prevent an en exception thrown caused by the user
// entering an invalid IP Address or Port number.
if (listener != null)
{
// Stop listening for new clients.
listener.Stop();
}
}
}
MessageBox.Show("CancellationRequested");
log.Info("TCP Server IN CancellationRequested");
}, cancelToken);
}
Interesting to see that no one had come back with any solutions, admittedly it took me a long while to figure out a solution. The key to stopping the TCP Listener when using a synchronous blocking mode like the example below is to register the Cancellation Token with the TCP Listener itself, as well the TCP Client that may have already been connected at the time the Cancellation Token was fired. (see comments that are marked as IMPORTANT)
The example code may differ slightly in your own environment and I have extracted some code bloat that is unique to my project, but you'll get the idea in what we're doing here. In my project this TCP Server is started as a background service using NET Core 5.0 IHosted Services. My code below was adapted from the notes on MS Docs: https://learn.microsoft.com/en-us/dotnet/api/system.net.sockets.tcplistener?view=net-5.0
The main difference between the MS Docs and my example below is I wanted to allow multiple TCP Clients to connect hence the reason why I start up a new inner Task each time a new TCP Client connects.
/// <summary>
/// </summary>
/// <param name="server"></param>
/// <param name="port"></param>
/// <param name="logger"></param>
/// <param name="cancelToken"></param>
public void TcpServerRun(
int pluginId,
string pluginName,
string encoding,
int bufferForReadingData,
string ipAddress,
int port,
bool logEvents,
IServiceScopeFactory _scopeFactory,
CancellationToken cancelToken)
{
IPAddress localAddrIN = IPAddress.Parse(ipAddress);
TcpListener listener = new TcpListener(localAddrIN, port);
Task.Run(() =>
{
// Dispose the DbContext instance when the task has completed. 'using' = dispose when finished...
using var scope = _scopeFactory.CreateScope();
var logger = scope.ServiceProvider.GetRequiredService<ILogger<TcpServer>>();
try
{
listener.Start();
cancelToken.Register(listener.Stop); // THIS IS IMPORTANT!
string logData = "TCP Server with name [" + pluginName + "] started Succesfully";
// Custom Logger - you would use your own logging method here...
WriteLogEvent("Information", "TCP Servers", "Started", pluginName, logData, null, _scopeFactory);
while (!cancelToken.IsCancellationRequested)
{
TcpClient client = listener.AcceptTcpClient();
logData = "A TCP Client with IP Address [" + client.Client.RemoteEndPoint.ToString() + "] connected to the TCP Server with name: [" + pluginName + "]";
// Custom Logger - you would use your own logging method here...
WriteLogEvent("Information", "TCP Servers", "Connected", pluginName, logData, null, _scopeFactory);
// Once each client has connected, start a new task with included parameters.
var task = Task.Run(async () =>
{
// Get a stream object for reading and writing
NetworkStream stream = client.GetStream();
// Buffer for reading data
Byte[] bytes = new Byte[bufferForReadingData]; // Bytes variable
String data = null;
int i;
cancelToken.Register(client.Close); // THIS IS IMPORTANT!
// Checks CanRead to verify that the NetworkStream is readable.
if (stream.CanRead)
{
// Loop to receive all the data sent by the client.
while ((i = stream.Read(bytes, 0, bytes.Length)) != 0 & !cancelToken.IsCancellationRequested)
{
data = Encoding.ASCII.GetString(bytes, 0, i);
logData = "TCP Server with name [" + pluginName + "] received data [" + data + "] from a TCP Client with IP Address [" + client.Client.RemoteEndPoint.ToString() + "]";
// Custom Logger - you would use your own logging method here...
WriteLogEvent("Information", "TCP Servers", "Receive", pluginName, logData, null, _scopeFactory);
}
// Shutdown and end connection
client.Close();
logData = "A TCP Client disconnected from the TCP Server with name: [" + pluginName + "]";
// Custom Logger - you would use your own logging method here...
WriteLogEvent("Information", "TCP Servers", "Disconnected", pluginName, logData, null, _scopeFactory);
}
}, cancelToken);
}
}
catch (SocketException ex)
{
// When the cancellation token is called, we will always encounter
// a socket exception for the listener.AcceptTcpClient(); blocking
// call in the while loop thread. We want to catch this particular exception
// and mark the exception as an accepted event without logging it as an error.
// A cancellation token is passed usually when the running thread is manually stopped
// by the user from the UI, or will occur when the IHosted service Stop Method
// is called during a system shutdown.
// For all other unexpected socket exceptions we provide en error log underneath
// in the else statement block.
if (ex.SocketErrorCode == SocketError.Interrupted)
{
string logData = "TCP Server with name [" + pluginName + "] was stopped due to a CancellationTokenSource cancellation. This event is triggered when the SMTP Server is manually stopped from the UI by the user or during a system shutdown.";
WriteLogEvent("Information", "TCP Servers", "Stopped", pluginName, logData, null, _scopeFactory);
}
else
{
string logData = "TCP Server with name [" + pluginName + "] encountered a socket exception error and exited the running thread.";
WriteLogEvent("Error", "TCP Servers", "Socket Exception", pluginName, logData, ex, _scopeFactory);
}
}
finally
{
// Call the Stop method to close the TcpListener.
// Closing the listener does not close any exisiting connections,
// simply stops listening for new connections, you are responsible
// closing the existing connections which we achieve by registering
// the cancel token with the listener.
listener.Stop();
}
});
}
I am using Linphone SDK in Xamarin.forms project for the sip calling. I am able to make the connection using following code:
var authInfo = Factory.Instance.CreateAuthInfo(username.Text,
null, password.Text, null, null,domain.Text);
LinphoneCore.AddAuthInfo(authInfo);
String proxyAddress ="sip:"+username.Text+"#192.168.1.180:5160";
var identity = Factory.Instance.CreateAddress(proxyAddress);
var proxyConfig = LinphoneCore.CreateProxyConfig();
identity.Username = username.Text;
identity.Domain = domain.Text;
identity.Transport = TransportType.Udp;
proxyConfig.Edit();
proxyConfig.IdentityAddress = identity;
proxyConfig.ServerAddr = domain.Text + ":5160;transport=udp";
proxyConfig.Route = domain.Text;
proxyConfig.RegisterEnabled = true;
proxyConfig.Done();
LinphoneCore.AddProxyConfig(proxyConfig);
LinphoneCore.DefaultProxyConfig = proxyConfig;
LinphoneCore.RefreshRegisters();
After Successful connection, I am using the code for placing the code.
if (LinphoneCore.CallsNb == 0)
{
string phoneCall = "sip:"+address.Text+ "#192.168.1.180:5160";
var addr = LinphoneCore.InterpretUrl(phoneCall);
LinphoneCore.InviteAddress(addr);
}
else
{
Call call = LinphoneCore.CurrentCall;
if (call.State == CallState.IncomingReceived)
{
LinphoneCore.AcceptCall(call);
}
else
{
LinphoneCore.TerminateAllCalls();
}
}
And the listener that is listening to call state changed event is as:
private void OnCall(Core lc, Call lcall, CallState state, stringmessage)
{
call_status.Text = "Call state changed: " + state;
if (lc.CallsNb > 0)
{
if (state == CallState.IncomingReceived)
{
call.Text = "Answer Call (" + lcall.RemoteAddressAsString + ")";
}
else
{
call.Text = "Terminate Call";
}
if (lcall.CurrentParams.VideoEnabled) {
video.Text = "Stop Video";
} else {
video.Text = "Start Video";
}
}
else
{
call.Text = "Start Call";
call_stats.Text = "";
}
}
The call status is giving 'Internal Server Error'. I am able to receive the calls using Linphone or X-lite Soft Phone in my code, But I am not able to place the calls. I don't know whether this issue is related to server or it is related to my code. Please suggest.
Internal Server Error (HTTP Status code 500) means that an unexpected error occurred on the server. So I would suspect the problem is rather there than with your app's code.
500 - A generic error message, given when an unexpected condition was encountered and no more specific message is suitable.
It could be that your request doesn't satisfy the expectations of the endpoint you are calling, but even then, the server should then respond with a more meaningful error, than crashing with 500.
I am using PushStreamContent to keep a persistent connection to each client. Pushing short heartbeat messages to each client stream every 20 seconds works great with 100 clients, but at about 200 clients, the client first starts receiving it a few seconds delayed, then it doesn't show up at all.
My controller code is
// Based loosely on https://aspnetwebstack.codeplex.com/discussions/359056
// and http://blogs.msdn.com/b/henrikn/archive/2012/04/23/using-cookies-with-asp-net-web-api.aspx
public class LiveController : ApiController
{
public HttpResponseMessage Get(HttpRequestMessage request)
{
if (_timer == null)
{
// 20 second timer
_timer = new Timer(TimerCallback, this, 20000, 20000);
}
// Get '?clientid=xxx'
HttpResponseMessage response = request.CreateResponse();
var kvp = request.GetQueryNameValuePairs().Where(q => q.Key.ToLower() == "clientid").FirstOrDefault();
string clientId = kvp.Value;
HttpContext.Current.Response.ClientDisconnectedToken.Register(
delegate(object obj)
{
// Client has cleanly disconnected
var disconnectedClientId = (string)obj;
CloseStreamFor(disconnectedClientId);
}
, clientId);
response.Content = new PushStreamContent(
delegate(Stream stream, HttpContent content, TransportContext context)
{
SaveStreamFor(clientId, stream);
}
, "text/event-stream");
return response;
}
private static void CloseStreamFor(string clientId)
{
Stream oldStream;
_streams.TryRemove(clientId, out oldStream);
if (oldStream != null)
oldStream.Close();
}
private static void SaveStreamFor(string clientId, Stream stream)
{
_streams.TryAdd(clientId, stream);
}
private static void TimerCallback(object obj)
{
DateTime start = DateTime.Now;
// Disable timer
_timer.Change(Timeout.Infinite, Timeout.Infinite);
// Every 20 seconds, send a heartbeat to each client
var recipients = _streams.ToArray();
foreach (var kvp in recipients)
{
string clientId = kvp.Key;
var stream = kvp.Value;
try
{
// ***
// Adding this Trace statement and running in debugger caused
// heartbeats to be reliably flushed!
// ***
Trace.WriteLine(string.Format("** {0}: Timercallback: {1}", DateTime.Now.ToString("G"), clientId));
WriteHeartBeat(stream);
}
catch (Exception ex)
{
CloseStreamFor(clientId);
}
}
// Trace... (this trace statement had no effect)
_timer.Change(20000, 20000); // re-enable timer
}
private static void WriteHeartBeat(Stream stream)
{
WriteStream(stream, "event:heartbeat\ndata:-\n\n");
}
private static void WriteStream(Stream stream, string data)
{
byte[] arr = Encoding.ASCII.GetBytes(data);
stream.Write(arr, 0, arr.Length);
stream.Flush();
}
private static readonly ConcurrentDictionary<string, Stream> _streams = new ConcurrentDictionary<string, Stream>();
private static Timer _timer;
}
Could there be some ASP.NET or IIS setting that affects this? I am running on Windows Server 2008 R2.
UPDATE:
Heartbeats are reliably sent if 1) the Trace.WriteLine statement is added, 2) Visual Studio 2013 debugger is attached and debugging and capturing the Trace.WriteLines).
Both of these are necessary; if the Trace.WriteLine is removed, running under the debugger has no effect. And if the Trace.WriteLine is there but the program is not running under the debugger (instead SysInternals' DbgView is showing the trace messages), the heartbeats are unreliable.
UPDATE 2:
Two support incidents with Microsoft later, here are the conclusions:
1) The delays with 200 clients were resolved by using a business class Internet connection instead of a Home connection
2) whether the debugger is attached or not really doesn't make any difference;
3) The following two additions to web.config are required to ensure heartbeats are sent timely, and failed heartbeats due to client disconnecting "uncleanly" (e.g. by unplugging computer rather than normal closing of program which cleanly issues TCP RST) trigger a timely ClientDisconnected callback as well:
<httpRuntime executionTimeout="5" />
<serverRuntime appConcurrentRequestLimit="50000" uploadReadAheadSize="1" frequentHitThreshold="2147483647" />
I am writing a kind of chat server app where a message received from one websocket client is sent out to all other websocket clients. To do this, I keep the connected clients in a list. When a client disconnects, I need to remove it from the list (so that future "sends" do not fail).
However, sometimes when a client disconnects, the server just gets an exception "connection reset by peer", and the code does not get chance to remove from the client list. Is there a way to guarantee a "nice" notification that the connection has been reset?
My code is:
void WsRequestHandler::handleRequest(HTTPServerRequest &req, HTTPServerResponse &resp)
{
int n;
Poco::Timespan timeOut(5,0);
try
{
req.set("Connection","Upgrade"); // knock out any extra tokens firefox may send such as "keep-alive"
ws = new WebSocket(req, resp);
ws->setKeepAlive(false);
connectedSockets->push_back(this);
do
{
flags = 0;
if (!ws->poll(timeOut,Poco::Net::Socket::SELECT_READ || Poco::Net::Socket::SELECT_ERROR))
{
// cout << ".";
}
else
{
n = ws->receiveFrame(buffer, sizeof(buffer), flags);
if (n > 0)
{
if ((flags & WebSocket::FRAME_OP_BITMASK) == WebSocket::FRAME_OP_BINARY)
{
// process and send out to all other clients
DoReceived(ws, buffer, n);
}
}
}
}
while ((flags & WebSocket::FRAME_OP_BITMASK) != WebSocket::FRAME_OP_CLOSE);
// client has closed, so remove from list
for (vector<WsRequestHandler *>::iterator it = connectedSockets->begin() ; it != connectedSockets->end(); ++it)
{
if (*it == this)
{
connectedSockets->erase(it);
logger->information("Connection closed %s", ws->peerAddress().toString());
break;
}
}
delete(ws);
ws = NULL;
}
catch (WebSocketException& exc)
{
//never gets called
}
}
See receiveFrame() documentation:
Returns the number of bytes received. A return value of 0 means that the peer has shut down or closed the connection.
So if receiveFrame() call returns zero, you can act acordingly.
I do not know if this is an answer to the question, but the implementation you have done does not deal with PING frames. This is currently (as of my POCO version: 1.7.5) not done automatically by the POCO framework. I put up a question about that recently. According to the RFC (6465), the ping and pong frames are used (among others) as a keep-alive function. This may therefore be critical to get right in order to get your connection stable over time. Much of this is guess-work from my side as I am experimenting with this now myself.
#Alex, you are a main developer of POCO I believe, a comment on my answer would be much appreciated.
I extended the catch, to do some exception handling for "Connection reset by peer".
catch (Poco::Net::WebSocketException& exc)
{
// Do something
}
catch (Poco::Exception& e)
{
// This is where the "Connection reset by peer" lands
}
A bit late to the party here... but I am using Poco and Websockets as well - and properly handling disconnects was tricky.
I ended up implementing a simple ping functionality myself where the client side sends an ACK message for every WS Frame it receives. A separate thread on the server side tries to read the ACK messages - and it will now detect when the client has disconnected by looking at flags | WebSocket::FRAME_OP_CLOSE.
//Serverside - POCO. Start thread for receiving ACK packages. Needed in order to detect when websocket is closed!
thread t0([&]()->void{
while((!KillFlag && ws!= nullptr && flags & WebSocket::FRAME_OP_BITMASK) != WebSocket::FRAME_OP_CLOSE && machineConnection != nullptr){
try{
if(ws == nullptr){
return;
}
if(ws->available() > 0){
int len = ws->receiveFrame(buffer, sizeof(buffer), flags);
}
else{
Util::Sleep(10);
}
}
catch(Poco::Exception &pex){
flags = flags | WebSocket::FRAME_OP_CLOSE;
return;
}
catch(...){
//log::info(string("Unknown exception in ACK Thread drained"));
return;
}
}
log::debug("OperatorWebHandler::HttpRequestHandler() Websocket Acking thread DONE");
});
on the client side I just send a dummy "ACK" message back to the server (JS) every time I receive a WS frame from the server (POCO).
websocket.onmessage = (evt) => {
_this.receivedData = JSON.parse(evt.data);
websocket.send("ACK");
};
It is not about disconnect handling, rather about the stability of the connection.
Had some issues with POCO Websocket server in StreamSocket mode and C# client. Sometimes the client sends Pong messages with zero length payload and disconnect occurs so I added Ping and Pong handling code.
int WebSocketImpl::receiveBytes(void* buffer, int length, int)
{
char mask[4];
bool useMask;
_frameFlags = 0;
for (;;) {
int payloadLength = receiveHeader(mask, useMask);
int frameOp = _frameFlags & WebSocket::FRAME_OP_BITMASK;
if (frameOp == WebSocket::FRAME_OP_PONG || frameOp ==
WebSocket::FRAME_OP_PING) {
std::vector<char> tmp(payloadLength);
if (payloadLength != 0) {
receivePayload(tmp.data(), payloadLength, mask, useMask);
}
if (frameOp == WebSocket::FRAME_OP_PING) {
sendBytes(tmp.data(), payloadLength, WebSocket::FRAME_OP_PONG);
}
continue;
}
if (payloadLength <= 0)
return payloadLength;
if (payloadLength > length)
throw WebSocketException(Poco::format("Insufficient buffer for
payload size %d", payloadLength),
WebSocket::WS_ERR_PAYLOAD_TOO_BIG);
return receivePayload(reinterpret_cast<char*>(buffer), payloadLength,
mask, useMask);
}
}