I have a QTCPServer receiver that is receiving different streams of data
Each QDataStream is received at fixed intervals i.e. 10 Hz and 1Hz
Out of all these data streams, two streams are received at same 10Hz rate
Issue: Since dataRate is the same on sending side, every time one of the stream is missed at receiving side.
It is just a sample code so please ignore typos or syntax errors.
Sender Side :
timer1.setInterval(1000) with Message_Id = 1
timer2.setInterval(100) with Message_Id = 2
timer3.setInterval(100) with Message_Id = 3
//data is sent in the timer Handlder
//data is sent successfully and cross-checked
Receiver Side:
QByteArray array;
QDataStream stream(&array:QIODevice:ReadOnly)
array = tcpServerConnection->readAll()
MyMessageType message;
stream >> message;
switch(message.id){
case 1:{
MessageType1 message1;
stream >> message1;}
break;
case 2:{
MessageType2 message2;
stream >> message2;}
break;
case 3:{
MessageType3 message3;
stream >> message3;}
break;}}
So in this case, if Message2 and Message3 have the same timer intervals, only one of them is received. Individually every message is received just fine.
Also with different random intervals, each message is received just fine.
What can be the issue with the same time intervals when sending a Qdatastream?
Related
The following scenario：
Sender have sent continuous 10000 bytes
Receiver ACK 0 - 8000(sender have recived those acks)
Now, Sender will send a reset frame, the question is how to set the " final size"
a. final size is 10000
b. final size is 8000
Looking at RFC 9000(https://datatracker.ietf.org/doc/html/rfc9000#section-4.5) witch
describing:
4.5. Stream Final Size
The final size is the amount of flow control credit that is
consumed by a stream. Assuming that every contiguous byte on the
stream was sent once, the final size is the number of bytes sent.
More generally, this is one higher than the offset of the byte with
the largest offset sent on the stream, or zero if no bytes were
sent.
I think the final size should be 10000, and sender must not send any more(transmission and
retransmission) on the identified stream, am I right?
https://datatracker.ietf.org/doc/html/rfc9000#section-19.4
After sending a RESET_STREAM, an endpoint ceases transmission and
retransmission of STREAM frames on the identified stream. A receiver
of RESET_STREAM can discard any data that it already received on that
stream.
And nginx'iquic may have some problems, nginx will retranmit frames when nginx have sent a reset frame(for example: nginx http3 have sent all data to ctx->frames, then qs will be deleted)
void
ngx_quic_resend_frames(ngx_connection_t *c, ngx_quic_send_ctx_t *ctx)
{
case NGX_QUIC_FT_STREAM:
qs = ngx_quic_find_stream(&qc->streams.tree, f->u.stream.stream_id);
if (qs) {
if (qs->send_state == NGX_QUIC_STREAM_SEND_RESET_SENT
|| qs->send_state == NGX_QUIC_STREAM_SEND_RESET_RECVD)
{
ngx_quic_free_frame(c, f);
break;
}
}
}
The final size is definitely 10000, as flow control credit is consumed by sending data on a stream; whether it is acknowlegded or not does not matter.
Indeed, after sending the reset-stream frame:
no new data should be send (this would be a violation of the final size leading to a fatal error as described in section 4.5
no retransmissions should be performed
The 3rd question is unclear to me. I'm not a ngx-quic expert, but from the code it posted i would guess it does not retransmit, as the frame is freed ;-)
I'm trying to send data of 2 sensors from arduino uno to NodeMCU V3 via serial communication,
when I try to send data from one sensor at the time everything works fine but when I use both it gives me random values
This is the arduino sender code :
int water_sensor_pin = 8;
void setup()
{ pinMode(water_sensor_pin, INPUT);
Serial.begin(115200);
}
void loop()
{
// First sensor
int soil_moisture=analogRead(A0);
int output_value = map(soil_moisture,430,70,0,100);
Serial.write(output_value);
// Second sensor
int value = digitalRead(water_sensor_pin);
if(value==HIGH){
Serial.write('1');}
if(value==LOW){
Serial.write('0');}
}
and this is the receiver's part of code
char msg[10];
.
.
.
if(Serial.available()>0){
// First sensor
int output_value = Serial.read();
Serial.println(output_value );
// Second sensor
char value = Serial.read();
Serial.println(value);
}
I expect the output to be correct values for both sensors
When using Serial in Arduino, you have to take care of sending a known amount of bytes and then read this amount of bytes.
On the transmitting side try something like Serial.write(output_value,4); in order to send four bytes and, on the receiving side, Serial.readBytes(output_value,4); in order to read the four bytes you sent, and only them.
Of course you can apply the same technic for the second value you want to send except that you may need only one byte as you seem to send a boolean.
Hope it helps!
EDIT
The technic above would work if you had a buffer of bytes to send. Unfortunately you have an integer value… So you can either try to:
convert your value as an array of char of a known size,
use the fact that the value you are trying to send can fit in a single byte and thus declaring it as a byte instead of an int and then reading this single byte on the receiver side.
I'll go right to the point. My arduino reads values from the adc port and send them via serial port(values from 0 to 255). I save them in a byte type vector. After sending an specific signal to arduino, it starts to send to Qt app the data saved in the vector. Everything is working except that the arduino should send 800 values and the app receives less values than that. If I set the serial baud rate to 9600, I get 220 values. If, instead, I set the baud rate to 115200, I get only 20 values. Can you guys help me to fix this? I would like to use 115200 baud rate, because I need a good trasmision speed at this project(Real time linear CCD). I'll leave some code below:
Arduino code:
void sendData(void)
{
int x;
for (x = 0; x < 800; ++x)
{
Serial.print(buffer[x]);
}
}
This is the function that sends the values. I think is enough information, so I summarized it. If you need more code, please let me know.
Qt serial port setting code:
...
// QDialog windows private variables and constants
QSerialPort serial;
QSerialPortInfo serialInfo;
QList<QSerialPortInfo> listaPuertos;
bool estadoPuerto;
bool dataAvailable;
const QSerialPort::BaudRate BAUDRATE = QSerialPort::Baud9600;
const QSerialPort::DataBits DATABITS = QSerialPort::Data8;
const QSerialPort::Parity PARITY = QSerialPort::NoParity;
const QSerialPort::StopBits STOPBITS = QSerialPort::OneStop;
const QSerialPort::FlowControl FLOWCONTROL = QSerialPort::NoFlowControl;
const int pixels = 800;
QVector<double> data;
unsigned int dataIndex;
QByteArray values;
double maximo;
...
// Signal and slot connection.
QObject::connect(&serial, SIGNAL(readyRead()), this,SLOT(fillDataBuffer()));
...
// Method called when there's data available to read at the serial port.
void Ventana::fillDataBuffer()
{
dataIndex++;
data.append(QString::fromStdString(serial.readAll().toStdString()).toDouble());
if(data.at(dataIndex-1) > maximo) maximo = data.at(dataIndex-1);
/* The following qDebug is the one I use to test the recieved values,
* where I check that values. */
qDebug() << data.at(dataIndex-1);
}
Thanks and sorry if it's not so clear, it has been an exhausting day :P
Ok... I see two probelms here:
Arduino side: you send your data in a decimal form (so x = 100 will be sent as 3 characters - 1, 0 and 0. You have no delimiter between your data, so how your receiver will know that it received value 100 not three values 1, 0 and 0? Please see my answer here for further explanation on how to send ADC data from Arduino.
QT side: There is no guarantee on the moment when readyRead() signal will be triggered. It may be immediately after first sample arrives, but it may be raised after there are already couple of samples inside the serial port buffer. If that happens, your method fillDataBuffer() may process string 12303402 instead of four separate strings 123, 0, 340 and 2, because between two buffer reads four samples arrived. The bigger the baudrate, the more samples will arrive between the reads, which is why you observe less values with a bigger baud rate.
Solution for both of your problems is to append some delimiting byte for your data, and split the string in the buffer on that delimiting byte. If you don't want to have maximum data throughput, you can just do
Serial.print(buffer[x]);
Serial.print('\n');
and then, split incoming string on \n character.
Thank you very much! I did what you said about my arduino program and after solving that, I was still not getting the entire amount of data. So the the problem was in Qt. How you perfectly explain, the serial buffer was accumulating the values too fast, so the slot function "fillDataBuffer()" was too slow to process the arriving data. I simplified that function:
void Ventana::fillDataBuffer()
{
dataIndex++;
buffer.append(serial.readAll());
}
After saving all the values in the QByteArray buffer, I process the data separately.
Thanks again man. Your answer was really helpful.
We have two Qt applications. App1 accepts a connection from App2 through QTcpServer and stores it in an instance of QTcpSocket* tcpSocket. App1 runs a simulation with 30 Hz. For each simulation run, a QByteArray consisting of a few kilobytes is sent using the following code (from the main/GUI thread):
QByteArray block;
/* lines omitted which write data into block */
tcpSocket->write(block, block.size());
tcpSocket->waitForBytesWritten(1);
The receiver socket listens to the QTcpSocket::readDataBlock signal (in main/GUI thread) and prints the corresponding time stamp to the GUI.
When both App1 and App2 run on the same system, the packages are perfectly in sync. However when App1 and App2 are run on different systems connected through a network, App2 is no longer in sync with the simulation in App2. The packages come in much slower. Even more surprising (and indicating our implementation is wrong) is the fact that when we stop the simulation loop, no more packages are received. This surprises us, because we expect from the TCP protocol that all packages will arrive eventually.
We built the TCP logic based on Qt's fortune example. The fortune server, however, is different, because it only sends one package per incoming client. Could someone identify what we have done wrong?
Note: we use MSVC2012 (App1), MSVC2010 (App2) and Qt 5.2.
Edit: With a package I mean the result of a single simulation experiment, which is a bunch of numbers, written into QByteArray block. The first bits, however, contain the length of the QByteArray, so that the client can check whether all data has been received. This is the code which is called when the signal QTcpSocket::readDataBlock is emitted:
QDataStream in(tcpSocket);
in.setVersion(QDataStream::Qt_5_2);
if (blockSize == 0) {
if (tcpSocket->bytesAvailable() < (int)sizeof(quint16))
return; // cannot yet read size from data block
in >> blockSize; // read data size for data block
}
// if the whole data block is not yet received, ignore it
if (tcpSocket->bytesAvailable() < blockSize)
return;
// if we get here, the whole object is available to parse
QByteArray object;
in >> object;
blockSize = 0; // reset blockSize for handling the next package
return;
The problem in our implementation was caused by data packages being piled up and incorrect handling of packages which had only arrived partially.
The answer goes in the direction of Tcp packets using QTcpSocket. However this answer could not be applied in a straightforward manner, because we rely on QDataStream instead of plain QByteArray.
The following code (run each time QTcpSocket::readDataBlock is emitted) works for us and shows how a raw series of bytes can be read from QDataStream. Unfortunately it seems that it is not possible to process the data in a clearer way (using operator>>).
QDataStream in(tcpSocket);
in.setVersion(QDataStream::Qt_5_2);
while (tcpSocket->bytesAvailable())
{
if (tcpSocket->bytesAvailable() < (int)(sizeof(quint16) + sizeof(quint8)+ sizeof(quint32)))
return; // cannot yet read size and type info from data block
in >> blockSize;
in >> dataType;
char* temp = new char[4]; // read and ignore quint32 value for serialization of QByteArray in QDataStream
int bufferSize = in.readRawData(temp, 4);
delete temp;
temp = NULL;
QByteArray buffer;
int objectSize = blockSize - (sizeof(quint16) + sizeof(quint8)+ sizeof(quint32));
temp = new char[objectSize];
bufferSize = in.readRawData(temp, objectSize);
buffer.append(temp, bufferSize);
delete temp;
temp = NULL;
if (buffer.size() == objectSize)
{
//ready for parsing
}
else if (buffer.size() > objectSize)
{
//buffer size larger than expected object size, but still ready for parsing
}
else
{
// buffer size smaller than expected object size
while (buffer.size() < objectSize)
{
tcpSocket->waitForReadyRead();
char* temp = new char[objectSize - buffer.size()];
int bufferSize = in.readRawData(temp, objectSize - buffer.size());
buffer.append(temp, bufferSize);
delete temp;
temp = NULL;
}
// now ready for parsing
}
if (dataType == 0)
{
// deserialize object
}
}
Please not that the first three bytes of the expected QDataStream are part of our own procotol: blockSize indicates the number of bytes for a complete single package, dataType helps deserializing the binary chunk.
Edit
For reducing the latency of sending objects through the TCP connection, disabling packet bunching was very usefull:
// disable Nagle's algorithm to avoid delay and bunching of small packages
tcpSocketPosData->setSocketOption(QAbstractSocket::LowDelayOption,1);
I'm trying to read variable streams of characters and process them on the Arduino once a certain string of bytes is read on the Arduino. I have a sample sketch like the following, but I can't figure out how to compare the "readString" to process something on the Arduino. I would like the Arduino to process "commands" such as {blink}, {open_valve}, {close_valve}, etc.
// Serial - read bytes into string variable for string
String readString;
// Arduino serial read - example
int incomingByte;
// flow_A LED
int led = 4;
void setup() {
Serial.begin(2400); // Open serial port and set Baud rate to 2400.
Serial.write("Power on test");
}
void loop() {
while (Serial.available()) {
delay(10);
if (Serial.available() > 0) {
char c = Serial.read(); // Gets one byte from serial buffer
readString += c; // Makes the string readString
}
}
if (readString.length() > 0) {
Serial.println( readString); // See what was received
}
if (readString == '{blink_Flow_A}') {
digitalWrite(led, HIGH); // Turn the LED on (HIGH is the voltage level).
delay(1000); // Wait for one second.
digitalWrite(led, LOW); // Turn the LED off by making the voltage LOW.
delay(1000); // Wait for a second.
}
Some definitions first:
SOP = Start Of Packet (in your case, an opening brace)
EOP = End Of Packet (in your case, a closing brace)
PAYLOAD = the characters between SOP and EOP
PACKET = SOP + PAYLOAD + EOP
Example:
PACKET= {Abc}
SOP = {
EOP = }
PAYLOAD = Abc
Your code should process one character at a time, and should be structured as a state machine.
When the code starts, the parser state is "I'm waiting for the SOP character". While in this state, you throw away every character you receive unless it's equal to SOP.
When you find you received a SOP char, you change the parser state to "I'm receiving the payload". You store every character from now on into a buffer, until you either see an EOP character or exhaust the buffer (more on this in a moment). If you see the EOP char, you "close" the buffer by appending a NULL character (i.e. 0x00) so that it becomes a standard NULL-terminated C-string, and you can work on it with the standard functions (strcmp, strstr, strchr, etc.).
At this point you pass the buffer to a "process()" function, which executes the operation specified by the payload (1)
You have to specify the maximum length of a packet, and size the receive buffer accordingly. You also have to keep track of the current payload length during the "payload receive" state, so you don't accidentally try to store more payload bytes into the temporary buffer than it can hold (otherwise you get memory corruption).
If you fill the receive buffer without seeing an EOP character, then that packet is either malformed (too long) or a transmission error changed the EOP character into something else. In either case you should discard the buffer contents and go back to "Waiting for SOP" state.
Depending on the protocol design, you could send an error code to the PC so the person typing at the terminal or the software on that side knows the last command it sent was invalid or not received correctly.
Finally, the blink code in you snipped should be replaced by non-blocking "blink-without-delay"-style code (look at the example that come with the Arduino IDE).
(1) Example of a "process" function:
void process(char* cmd) {
if (strcmp(cmd, "open_valve") == 0) {
open_valve();
}
else if (strcmp(cmd, "close_valve") == 0) {
close_valve();
}
else {
print_error("Unrecognized command.");
}
}
It seems you are comparing the string in this statement:
if( readString == '{blink_Flow_A}' )
So I don't get your question re :
but I can't figure out how to compare the "readString" to process something
Are you really asking:
How do I extract the commands from an incoming stream of characters?
If that is the case then treat each command as a "packet". The packet is enclosed in brackets: {}. Knowing that the {} brackets are start and end of a packet, it is easy to write a routine to get at the command in the packet.
Once the command is extracted just go through a if-then-else statement to do what each command is supposed to do.
If I totally misunderstood your question I apologize :)
EDIT:
see http://arduino.cc/en/Tutorial/StringComparisonOperators
if( readString == "{blink_Flow_A}" ) should be correct syntax.
Since you have a statement
Serial.println( readString);
you should see the string received.