I already do know, that it is impossible to simply detect if socket is disconnected or not - the server and clients must shout "Can you hear me?" and "Yeah I can." just like we do on skype.
But when boost::asio socket is disconnected from other side I obtain Unhanded exception when trying to read from socket. This is kind of disconnect detection useful enough for me. Can I handle that exception, so instead of crashing, the program will produce message in the console?
Some code for those who need it for everything:
bool SocketClient::read(int bytes, char *text) {
char buffer = 0;
int length = 0;
while(bytes>0) {
size_t len = sock.receive(boost::asio::buffer(&buffer, 1)); //boom: UNHANDLED EXCEPTION
bytes--;
text[length] = buffer;
length++;
}
return true;
}
Because I am connecting to minecraft server, I know when the client is disconnected - exception is caused on any read/write attempt.
try
{
size_t len = sock.receive(boost::asio::buffer(&buffer, 1)); //boom: UNHANDLED EXCEPTION
// More code ...
}
catch (const boost::system::system_error& ex)
{
if ( ex.code() == boost::asio::error::eof )
{
// Work your magic (console logging, retry , bailout etc.)
}
}
Please also take a look at the doc. In the worst case , you could infer the exception type from the debugger :)
Related
When client create an instant on SenderThread. It can send data to and from.
But when client goes for suspend mode and come back from suspend. The last created threads get exception on
resume. and no data is sent.
Exception Details received :
displayText = Exception
message =
name = Exception
className = N4Poco9ExceptionE
Here is the code:
class SenderThread: public Poco::Runnable
{
public:
MyThread(const std::string& msg):
Msg(msg);
{
}
void run()
{
try {
SendData(msg);
} catch(Exception exp) {
std::cout<<"displayText = "<<e.displayText()<<std::endl;
std::cout<<"message = "<<e.message()<<std::endl;
std::cout<<"name = "<<e.name()<<std::endl;
std::cout<<"className = "<<e.className()<<std::endl;
}
}
private:
std::string Msg;
};
How can I get more details on the exception and how to handle this exception?.
Edited After Günter Obiltschnig comment:
I am able to catch the proper exception.
displayText = Invalid argument
name = Invalid argument
Some time i see socket closed exception. When system goes to suspend mode then all the socket is closed by system(os). Now upon resume application tries to open the socket again it throw error in the Poco::Net::Socket::Socket(Poco::Net::Socket const&). any help on this please
You have to catch the exception by (const) reference in order to get useful information out of it.
catch (const Poco::Exception& exc)
{
std::cerr << exc.displayText() << std::endl;
}
I am trying to send some data by using boost socket.
TCPClient class's role is to make a connection cna can send data throw sendMessage method.
When I executed under code it does not work. However, it works when I debug it.
I think the problem is timing.
delete[] msg; works before sending msg.(just my thought)
so, I want to check whether msg is sent or not.
or any other good way.
client main() code
TCPClient *client = new TCPClient(ip, port);
client->sendMessage((char *)msg, 64 + headerLength + bodyLength);
delete[] msg;
under code is snedMessage method.
void TCPClient::sendMessage(const char *message, int totalLength) throw(boost::system::system_error) {
if(false == isConnected())
setConnection();
boost::system::error_code error;
this->socket.get()->write_some(boost::asio::buffer(message, totalLength), error);
if(error){
//do something
}
}
Your sendMessage() function is written incorrectly. You cannot expect that socket will send all of your data at once, you need a loop where you try to send, check how many bytes were sent, offset buffer (and update totalLength accordingly of course) if necessary and repeat until all data is sent. Or interrupt if there is error condition. You try to send only once, ignore result and assume that if there is no error then all data was sent. This is not a case. Stream socket may send one or two or whatever amount of bytes at a time, and your code needs to handle that.
Your code should be something like this:
while( totalLength ) {
boost::system::error_code error;
auto sz = this->socket.get()->write_some(boost::asio::buffer(message, totalLength), error);
if(error){
//do something and interrupt the loop
}
totalLength -= sz;
message += sz;
}
I have a server method that waits for new incoming TCP connections, for each connection I'm creating two threads (detached) for handling various tasks.
void MyClass::startServer(boost::asio::io_service& io_service, unsigned short port) {
tcp::acceptor TCPAcceptor(io_service, tcp::endpoint(tcp::v4(), port));
bool UARTToWiFiGatewayStarted = false;
for (;;) {
auto socket(std::shared_ptr<tcp::socket>(new tcp::socket(io_service)));
/*!
* Accept a new connected WiFi client.
*/
TCPAcceptor.accept(*socket);
socket->set_option( tcp::no_delay( true ) );
MyClass::enableCommunicationSession();
// start one worker thread.
std::thread(WiFiToUARTWorkerSession, socket, this->LINport, this->LINbaud).detach();
// only if this is the first connected client:
if(false == UARTToWiFiGatewayStarted) {
std::thread(UARTToWifiWorkerSession, socket, this->UARTport, this->UARTbaud).detach();
UARTToWiFiGatewayStarted = true;
}
}
}
This works fine for starting the communication, but the problem appears when the client disconnects and connects again (or at least tries to connect again).
When the current client disconnects, I stop the communication (by stopping the internal infinite loops from both functions, then they'll return).
void Gateway::WiFiToUARTWorkerSession(std::shared_ptr<tcp::socket> socket, ...) {
/*!
* various code here...
*/
try {
while(true == MyClass::communicationSessionStatus) {
/*!
* Buffer used for storing the UART-incoming data.
*/
unsigned char WiFiDataBuffer[max_incoming_wifi_data_length];
boost::system::error_code error;
/*!
* Read the WiFi-available data.
*/
size_t length = socket->read_some(boost::asio::buffer(WiFiDataBuffer), error);
/*!
* Handle possible read errors.
*/
if (error == boost::asio::error::eof) {
break; // Connection closed cleanly by peer.
}
else if (error) {
// this will cause the infinite loops from the both worker functions to stop, and when they stop the functions will return.
MyClass::disableCommunicationSession();
sleep(1);
throw boost::system::system_error(error); // Some other error.
}
uart->write(WiFiDataBuffer, length);
}
}
catch (std::exception &exception) {
std::cerr << "[APP::exception] Exception in thread: " << exception.what() << std::endl;
}
}
I expect that when I reconnect the communication should work again (the MyClass::startServer(...) will create and detach again two worker threads that will do the same things.
The problem is that when I connect the second time I get:
terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::system::system_error> >'
what(): write: Broken pipe
From what I found about this error it seems that the server (this application) sends something via TCP to a client that was disconnected.
What I'm doing wrong?
How can I solve this problem?
A read of length 0 with no error is also an indication of eof. The boost::asio::error::eof error code is normally more useful when you're checking the result of a composed operation.
When this error condition is missed, the code as presented will call write on a socket which has now been shutdown. You have used the form of write which does not take a reference to an error_code. This form will throw if there is an error. There will be an error. The read has failed.
i am creating client sever application in windows using socket and i want to throw exception at run time from thread if any problem occur but i am getting error for throw statement.
//create thread in cpp file
CreateThread(NULL,0,startServer,this,0,NULL);
//thread in header file
static unsigned long __stdcall startServer(void *i_SocketTransportServer)
{
((SocketTransportServer*)i_SocketTransportServer)->StartServerThread(((SocketTransportServer *)i_SocketTransportServer)->m_socketServer);
return 0;
}
//and StartServerThread is function called by thread
// SocketTransportServer is inner class of RMLThinTransport
void RMLThinTransport::SocketTransportServer::StartServerThread(SOCKET i_socketServer)
{
m_socketAccept=NULL;
while(true)
{
Sleep(20);
if(m_canAcceptMore)
{
m_canAcceptMore=false;
if(!m_isRunning)
{
break;
}
try
{
m_socketAccept=accept(m_socketServer,NULL,NULL);
if(m_socketAccept==INVALID_SOCKET)
{
int lastError=WSAGetLastError();
closesocket(m_socketAccept);
SocketExceptions
exceptionInAcceptAtServer;
exceptionInAcceptAtServer.detectErrorAccept(&lastError);
throw exceptionInAcceptAtServer;
}
else
{
//_LOG("Client connected",EventTypeInfo) ;
OutputDebugStringW(L"client connected.....");
/* If client connected then setClinetCout value 1 */
setClientCount(1);
m_ClientSockets.push_back(m_socketAccept);
CreateThread(NULL,0,receiveDataAtServer,this,0,NULL);
}
}
catch(SocketExceptions& i_exceptionInAcceptAtServer)
{
/*OutputDebugStringW(L"Can't accept client In Exception. ."); */
throw i_exceptionInAcceptAtServer;//getting runtime error from here
}
}
}
}
now i want to throw error when server close but i am getting run time error. so is there any way so i can get error in my main function.sorry but i am new in c++ so please help me. and error is
The code that throws the exception is not the problem; it's the lack of any code to catch the exception that's the problem. The application is terminating because nothing is catching the exception you're throwing; you must ensure that something is going to catch it. Your startServer method -- the thread procedure -- must catch the exception, and cleanly exit the thread.
I started to program client/server applications in J2ME recently.Now I'm working with c++ builder 2010 indy components (e.g. TidTTCPServer) and J2ME. My application is designed to restart the kerio winroute firewall service from a remote machine.
My server application is written in c++ builder 2010, I've put a TidTCTServer component into a form which binded to 127.0.0.1:4500. That's listening on port 4500 in local machine.
Then i've added a listbox that i need to add every upcoming packets converted to UnicodeString.
//void __fastcall TForm1::servExecute(TIdContext *AContext)
UnicodeString s;
UnicodeString txt;
txt=Trim(AContext->Connection->IOHandler->ReadLn());
otvet->Items->Add(txt);
otvet->ItemIndex=otvet->Items->Count-1;
if (txt=="1") {
AContext->Connection->IOHandler->WriteLn("Suhrob");
AContext->Connection->Disconnect();
}
if (txt=="2") {
AContext->Connection->IOHandler->WriteLn("Shodi");
AContext->Connection->Disconnect();
}
//----------------------------------------------------------------------------
// void __fastcall TForm1::servConnect(TIdContext *AContext)
++counter;
status->Panels->Items[0]->Text="Connections:" + IntToStr(counter);
status->Panels->Items[1]->Text="Connected to " + AContext->Connection->Socket->Binding->PeerIP + ":" + AContext->Connection->Socket->Binding->PeerPort;
and my client side code looks smth like this:
else if (command == send) {
// write pre-action user code here
InputStream is=null;
OutputStream os=null;
SocketConnection client=null;
ServerSocketConnection server=null;
try {
server = (ServerSocketConnection) Connector.open("socket://"+IP.getString()+":"+PORT.getString());
// wait for a connection
client = (SocketConnection) Connector.open("socket://"+IP.getString()+":"+PORT.getString());
// set application-specific options on the socket. Call setSocketOption to set other options
client.setSocketOption(SocketConnection.DELAY, 0);
client.setSocketOption(SocketConnection.KEEPALIVE, 0);
is = client.openInputStream();
os = client.openOutputStream();
// send something to server
os.write("texttosend".getBytes());
// read server response
int c = 0;
while((c = is.read()) != -1) {
// do something with the response
System.out.println((char)c);
}
// close streams and connection
}
catch( ConnectionNotFoundException error )
{
Alert alert = new Alert(
"Error", "Not responding!", null, null);
alert.setTimeout(Alert.FOREVER);
alert.setType(AlertType.ERROR);
switchDisplayable(alert, list);
}
catch (IOException e)
{
Alert alert = new Alert("ERror", e.toString(), null, null);
alert.setTimeout(Alert.FOREVER);
alert.setType(AlertType.ERROR);
switchDisplayable(alert, list);
e.printStackTrace();
}
finally {
if (is != null) {
try {
is.close();
} catch (Exception ex) {
System.out.println("Failed to close is!");
}
try {
os.close();
} catch (Exception ex) {
System.out.println("Failed to close os!");
}
}
if (server != null) {
try {
server.close();
} catch (Exception ex) {
System.out.println("Failed to close server!");
}
}
if (client != null) {
try {
client.close();
} catch (Exception ex) {
System.out.println("Failed to close client!");
}
}
}
my client application gets connected with the server but when i try to send data such as
os.write("texttosend".getBytes());
I cannot get text data on the server using. That's I am not getting sent packets in the server from client.
txt=Trim(AContext->Connection->IOHandler->ReadLn());
Guys, where am I wrong? is the way i'm doing is ok?
Or do I need to use StreamConnection instead of SocketConnection?
And when i use telnet to send data it works cool, strings will be added to listbox
telnet 127.0.0.1 4500
texttosend
23
asf
Any help is appreciated !!!
Thanks in advance!
The main problem is that you are using ReadLn() on the server end. ReadLn() does not exit until a data terminator is encountered (a LF line break character is the default terminator) or if a reading timeout occurs (Indy uses infinite timeouts by default). Your J2ME code is not sending any data terminator, so there is nothing to tell ReadLn() when to stop reading. The reason it works with Telnet is because it does send line break characters.
The other problem with your code is that TIdTCPServer is a multi-threaded component, but your code is updating the UI components in a thread-unsafe manner. You MUST synchronize with the main thread, such as by using Indy's TIdSync and/or TIdNotify classes, in order to update your UI safely from inside of the server's event handlers.
Yes, flush method is necessary to call after sending bytes, but ..... finally....
then i tried to include my connection code in a new thread that implements Runnable worked perfectly. Now I've found where I was wrong!!!!!!!!!!!!!!
That's guys you need to include above code in the following block.
Thread t= new Thread(this);
t.start();
public void run()
{
//here paste the code
}
Try OutputStream.flush()?
If not, try writing to a known working server, instead of one you've created yourself (something like writing "HELO" to an SMTP server), this will help you figure out which end the error is at.