I'm very new to mqtt c++ client.
i have a mqtt::async_client (documentation here) client with automatic reconnect options that I want to test but I am having difficulties in inducing a connection loss or connection interruptions.
Consider the following
/* mqtt async client connecting to localhost with
port 1833 and is called "client_name"
*/
mqtt::async_client cli("localhost", 1883, "client_name");
const mqtt::connect_options conOp;
/* set options to automatically reconnect after a connection loss(?)
at every 10 seconds interval upto 40 seconds
*/
conOpt.set_automatic_reconnect(10, 40);
/* establish the connection */
cli.connect(conOp);
/* induce connection interruption for 42 seconds? */
cli.interrupt_connection(42); //how to do this?
bool isConnected = true;
isConnected = cli->is_connected();
std::cout << "Is the client connected ? "<< isConnected << "\n";
stdcout should be false since the connection could not be established.
Any suggestions will be really helpful. Thanks in advance
Related
I've been working with a LilyGo-TCall-SIM800 module for several days, trying to get out of a dead end.
I have tried an example from "random nerd tutorials" which works correctly. The module connects to the internet and can send data to the cloud.
I have the problem to send AT commands to the SIM800L chip integrated in the module. I can't get the chip to react back.
I have tried using Serial1 and Serial2. I have also tried configuring the RX and TX transmission pins, and I have tried with different baudrates. Always with negative results... when sending the "AT\r" command to the SIM800L, it should return "OK". But it never does.
I have simplified the code as much as possible to minimize errors:
/*
Name: TestAT.ino
Created: 08/12/2022 23:15:28
Author: user
*/
// Set serial for debug console (to the Serial Monitor, speed 115200)
#define SerialMon Serial
// Comunications between ESP32 and SIM800L
#define SerialAT Serial1
//Comunications between ESP32 ans SIM800L go thought TX and RX pins on Serial1 Port
#define MODEM_RX1 16
#define MODEM_TX1 17
void setup() {
// Set console baud rate
SerialMon.begin(115200);
delay(1000);
//Set SerialAT baud rate
SerialAT.begin(38400, SERIAL_8N1, MODEM_RX1, MODEM_TX1);
//Set timeLimit for SerialAT reads
SerialAT.setTimeout(2000);
}
void loop() {
String returned = "";
char ATcommand[] = { 'A','T','\r' };
SerialAT.print(ATcommand);
delay(1000);
returned = SerialAT.readString();
SerialMon.print(millis());
SerialMon.print(" - ");
SerialMon.print(ATcommand);
SerialMon.print(" - SerialAT returned:");
SerialMon.println(returned);
}
Anybody can help me out on this? Any idea or sugestion?
Thanks in advance
I have two machines in the same network :
The first machine binds to a socket on its own IP address (120.0.0.1) and receives any data coming to the socket .bind()-ed on port 5555:
zmq::context_t context{1};
zmq::socket_t socket{context, ZMQ_SUB};
socket.setsockopt(ZMQ_SUBSCRIBE, "lidar");
socket.bind("tcp://120.0.0.1:5555");
while(true)
{
zmq::message_t message;
auto recv = socket.recv(message);
ROS_INFO("Value: %d", recv.value());
}
The second machine, having an IP address 120.0.0.248, connects to the first machine and sends the messages to it:
sock.connect("tcp://120.0.0.1:5555");
while (1) {
double nodes[8192];
sock.send(zmq::buffer("lidar") , zmq::send_flags::sndmore);
sock.send(zmq::buffer(nodes, (((int)(count)) * 8)));
}
But for some reason, I cannot receive any messages on the first machine and it gets stuck on auto recv = socket.recv(message);.
What is a correct way for such communication?
Test Scenario
I had written a windows program which I simply called it "simpleServer.exe". This program is just a simulation of a very basic server application. It listens on a port, and wait for incoming messages. The listening Socket was defined to be a TCP Stream Socket. that's all that this program is doing.
I had been deploying this exact same program on 2 different machines, both running on windows 7 professional 64bit. This machine will act as a host. and they are stationed in the same network area.
then, using the program "nmap", I used another machine on the same network, to act as a client. using the "-sS" parameter on "nmap", I do a Syn Scan, to the IP and Port of the listening simpleServer on both machine (one attempt at a time).
(note that the 2 hosts already had "wireshark" started, and is monitoring on tcp packets from the client's IP and to the listening port.)
In the "wireshark" entry, on both machine, I saw the expected tcp packet for Syn Scan:
client ----(SYN)----> host
client <--(SYN/ACK)-- host
client ----(RST)----> host
the above packet exchange suggests that the connection was not established.
But on the "simpleServer.exe", only one of it had "new incoming connection" printed in the logs, while the other instance was not alerted of any new incoming connection, hence no logs at all.
Code Snippets
iRetVal = WSAEventSelect (m_Socket, m_hSocketEvent, FD_ACCEPT);
if (SOCKET_ERROR == iRetVal)
{
if (WSAGetLastError()==WSAENOTSOCK)
{
return E_SOCKET_INVALID;
}
CHKLOGGER (m_pLogger->Log (LOGGER_LOG_ERROR,"GHLSocket::OnAccept() Error while WSAEventSelect(). Error code: ", WSAGetLastError() ));
#if defined GHLSOCKET_DEBUG_VERSION
printf ("Error while WSAEventSelect(). Error code: %ld\n", WSAGetLastError() );
#endif
return E_FAILED_RECV_DATA;
}
// Wait for Network Events to occcur
dwRetVal = WSAWaitForMultipleEvents ( 1,
&m_hSocketEvent,
FALSE,
lTimeout,
TRUE);
if ( WSA_WAIT_TIMEOUT == dwRetVal )
{
return E_TIMEOUT;
goto CleanUp;
}
if ( WSA_WAIT_FAILED == dwRetVal)
{
CHKLOGGER (m_pLogger->Log (LOGGER_LOG_ERROR,"GHLSocket::OnAccept() WSAWaitForMultipleEvents() failed. Error code: ", WSAGetLastError() ));
#if defined GHLSOCKET_DEBUG_VERSION
printf ("Error in WSAWaitForMultipleEvents() failed. Error code: %ld\n", WSAGetLastError() );
#endif
dwReturn = E_FAILED_RECV_DATA;
goto CleanUp;
}
// Parse the Results from the Network Events.
iRetVal = WSAEnumNetworkEvents (m_Socket, m_hSocketEvent, &mEvents);
if (SOCKET_ERROR == iRetVal)
{
CHKLOGGER (m_pLogger->Log (LOGGER_LOG_ERROR,"GHLSocket::OnAccept() Error while WSAEnumNetworkEvents(). Error code: ", WSAGetLastError() ));
#if defined GHLSOCKET_DEBUG_VERSION
printf ("Error while WSAEnumNetworkEvents(). Error code: %ld\n", WSAGetLastError() );
#endif
dwReturn = E_FAILED_RECV_DATA;
goto CleanUp;
}
// ACCEPT event Detected.
if (mEvents.lNetworkEvents & FD_ACCEPT)
{
// Perform accept operation.
*p_SOCKET = accept (m_Socket, NULL,NULL);
}
Help That I Needed
why is the different behavior from the 2 same of the same application on a different machine with the same OS?
I'm writing a small application with a client and a server - the client sends a question and the server answers.
I managed to do the first part - the server gets the question from the client, do some work and sends back an answer. I just can't figure out how to tell the client to wait for a response from the server.
This is my client code:
char* ipAddress = (char*)malloc(15);
wcstombs(ipAddress, (TCHAR*)argv[1], 15);
DWORD port = wcstod(argv[2], _T('\0'));
DWORD numOfThreads = wcstod(argv[3], _T('\0;'));
DWORD method = wcstod(argv[4], _T('\0;'));
//initialize windows sockets service
WSADATA wsaData;
int iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
assert(iResult==NO_ERROR);
//prepare server address
sockaddr_in server_addr;
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = inet_addr(ipAddress);
server_addr.sin_port = htons(port);
//create socket
SOCKET hClientSocket= socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
assert(hClientSocket!=INVALID_SOCKET);
//connect to server
int nRes=connect(hClientSocket, (SOCKADDR*)&server_addr, sizeof(server_addr));
assert(nRes!=SOCKET_ERROR);
char* buf = "GET /count.htm HTTP/1.1\r\nHost: 127.0.0.1:666\r\nAccept: text/html,application/xhtml+xml\r\nAccept-Language: en-us\r\nAccept-Encoding: gzip, deflate\r\nUser-Agent: Mozilla/5.0\r\n\r\n";
int nBytesToSend= strlen(buf);
int iPos=0;
while(nBytesToSend)
{
int nSent=send(hClientSocket,buf,nBytesToSend,0);
assert(nSent!=SOCKET_ERROR);
nBytesToSend-=nSent;
iPos+=nSent;
}
closesocket(hClientSocket);
int nLen = sizeof(server_addr);
SOCKET hRecvSocket=accept(hClientSocket,(SOCKADDR*)&server_addr, &nLen);
assert(hRecvSocket!=INVALID_SOCKET);
//prepare buffer for incoming data
char serverBuff[256];
int nLeft=sizeof(serverBuff);
iPos=0;
do //loop till there are no more data
{
int nNumBytes=recv(hRecvSocket,serverBuff+iPos,nLeft,0);
//check if cleint closed connection
if(!nNumBytes)
break;
assert(nNumBytes!=SOCKET_ERROR);
//update free space and pointer to next byte
nLeft-=nNumBytes;
iPos+=nNumBytes;
}while(1);
The assertion after the SOCKET hRecvSocket=accept(hClientSocket,(SOCKADDR*)&server_addr, &nLen); line fails.
The closesocket and accept call after your "send" loop - remove those calls. accept is for servers listening for incoming connections, not for clients that are already connected.
After your send() loop completes, go straight into your recv() loop. That should solve your immediate problem:
Also, your send loop is forgetting to referenece iPos on the buffer like I think you intended to. This is what you wanted:
int nSent=send(hClientSocket,buf+iPos,nBytesToSend,0);
In network programming, sockets will fail due to network conditions beyond your control. So "asserts" on network calls are not always appropriate. Better to just expect failure and be prepared to handle it. Typically, closing the socket and the active connection is the way to handle most errors.
I have an asynchronous socket and call to connect() + GetLastError() which returns WSA_WOULD_BLOCK, as expected. So I start "receiving/reading" thread and subscribe Event to FD_READ and FD_CLOSE.
The story is: connect will sequentially fail, since Server is not up and running. My understanding that my receiving thread should get FD_CLOSE soon and I need to follow-up with cleaning.
It does not happen. How soon should I receive FD_CLOSE? Is it proper approach? Is there any other way to understand that connect() failed? Shoul I ever receive FD_CLOSE if socket isn't connected?
I do start my receiving thread and subscribe event after successful call to DoConnect() and I am afraid that racing condition prevents me from getting FD_CLOSE.
Here is some code:
int RecvSocketThread::WaitForData()
{
int retVal = 0
while (!retVal)
{
// sockets to pool can be added on other threads.
// please validate that all of them in the pool are connected
// before doing any reading on them
retVal = DoWaitForData();
}
}
int RecvSocketThread::DoWaitForData()
{
// before waiting for incoming data, check if all sockets are connected
WaitForPendingConnection_DoForAllSocketsInThePool();
// other routine to read (FD_READ) or react to FD_CLOSE
// create array of event (each per socket) and wait
}
void RecvSocketThread::WaitForPendingConnection_DoForAllSocketsInThePool()
{
// create array and set it for events associated with pending connect sockets
HANDLE* EventArray = NULL;
int counter = 0;
EventArray = new HANDLE[m_RecvSocketInfoPool.size()];
// add those event whose associated socket is still not connected
// and wait for FD_WRITE and FD_CLOSE. At the end of this function
// don't forget to switch them to FD_READ and FD_CLOSE
while (it != m_RecvSocketInfoPool.end())
{
RecvSocketInfo* recvSocketInfo = it->second;
if (!IsEventSet(recvSocketInfo->m_Connected, &retVal2))
{
::WSAEventSelect(recvSocketInfo->m_WorkerSocket, recvSocketInfo->m_Event, FD_WRITE | FD_CLOSE);
EventArray[counter++] = recvSocketInfo->m_Event;
}
++it;
}
if (counter)
{
DWORD indexSignaled = WaitForMultipleObjects(counter, EventArray, WaitAtLeastOneEvent, INFINITE);
// no matter what is further Wait doen't return for failed to connect socket
if (WAIT_OBJECT_0 <= indexSignaled &&
indexSignaled < (WAIT_OBJECT_0 + counter))
{
it = m_RecvSocketInfoPool.begin();
while (it != m_RecvSocketInfoPool.end())
{
RecvSocketInfo* recvSocketInfo = it->second;
if (IsEventSet(recvSocketInfo->m_Event, NULL))
{
rc = WSAEnumNetworkEvents(recvSocketInfo->m_WorkerSocket,
recvSocketInfo->m_Event, &networkEvents);
// Check recvSocketInfo->m_Event using WSAEnumnetworkevents
// for FD_CLOSE using FD_CLOSE_BIT
if ((networkEvents.lNetworkEvents & FD_CLOSE))
{
recvSocketInfo->m_FD_CLOSE_Recieved = 1;
*retVal = networkEvents.iErrorCode[FD_CLOSE_BIT];
}
if ((networkEvents.lNetworkEvents & FD_WRITE))
{
WSASetEvent(recvSocketInfo->m_Connected);
*retVal = networkEvents.iErrorCode[FD_WRITE_BIT];
}
}
++it;
}
}
// if error - DoClean, if FD_WRITE (socket is writable) check if m_Connected
// before do any sending
}
}
You will not receive an FD_CLOSE notification if connect() fails. You must subscribe to FD_CONNECT to detect that. This is clearly stated in the connect() documentation:
With a nonblocking socket, the connection attempt cannot be completed
immediately. In this case, connect will return SOCKET_ERROR, and
WSAGetLastError will return WSAEWOULDBLOCK. In this case, there are
three possible scenarios:
•Use the select function to determine the completion of the
connection request by checking to see if the socket is writeable.
•If the application is using WSAAsyncSelect to indicate interest in
connection events, then the application will receive an FD_CONNECT
notification indicating that the connect operation is complete
(successfully or not).
•If the application is using WSAEventSelect to indicate interest in
connection events, then the associated event object will be signaled
indicating that the connect operation is complete (successfully or
not).
The result code of connect() will be in the event's HIWORD(lParam) value when LOWORD(lParam) is FD_CONNECT. If the result code is 0, connect() was successful, otherwise it will be a WinSock error code.
If you call connect() and get a blocking notification you have to write more code to monitor for connect() completion (success or failure) via one of three methods as described here.
With a nonblocking socket, the connection attempt cannot be completed
immediately. In this case, connect will return SOCKET_ERROR, and
WSAGetLastError will return WSAEWOULDBLOCK. In this case, there are
three possible scenarios:
•Use the select function to determine the completion of the connection
request by checking to see if the socket is writeable.
•If the
application is using WSAAsyncSelect to indicate interest in connection
events, then the application will receive an FD_CONNECT notification
indicating that the connect operation is complete (successfully or
not).
•If the application is using WSAEventSelect to indicate interest
in connection events, then the associated event object will be
signaled indicating that the connect operation is complete
(successfully or not).
I think I need to start Receving thread once socket handle is created, but before connect is called. It is too late to create it after connect was called on asynchronous socket.
For synchronous socket those two calls createsocket() and connect() was just two consequitive lines. Does not work for non-blocking.
In this case at the beginning of receiving thread I need to check for FD_CONNECT and/or FD_WRITE in order be informed of connect attempt status.