flutter_libserialport write OK but read unhandled exception - flutter

Question

I'm trying to implement a simple at cmd application.
I modified the flutter_libserialport example.
https://pub.dev/packages/flutter_libserialport
simply,
replace the floatButton action to my own reTest() function
floatingActionButton: FloatingActionButton(
child: Icon(Icons.refresh),
// onPressed: initPorts,
onPressed: rwTest,
),
and my rwTest below,
Future<void> rwTest() async {
for (var p in availablePorts) {
if (p == 'COM115') {
print(p);
List<int> d = [65, 84, 13];
Uint8List bytes = Uint8List.fromList(d);
SerialPort port = SerialPort(p);
SerialPortReader reader = SerialPortReader(port, timeout: 10000);
try {
port.openReadWrite();
print(port.write(bytes));
await reader.stream.listen((data) {
print('received : $data');
});
port.close();
} on SerialPortError catch (_, err) {
if (port.isOpen) {
port.close();
print('serial port error');
}
}
}
}
}
my device is shown as COM115 so I put the fixed value.
and the "write" operation was success
but when I use "reader.stream.listen()"
SerialPortError occurs as below
flutter: COM115
flutter: 3
[ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: SerialPortError: ÀÛ¾÷À» ¿Ï·áÇß½À´Ï´Ù., errno = 0
I guess the usage of "listen" was wrong, but I don't know how to fix it.
anyone can help me to fix it?

Answer 1

You just need to remove the port.close() in try{} ... and I think you should also set the timeout = 1,
Also, it is better to set a configuration before using the port
Note: you can just access the port through name, without looping over all the available ports.
Future<void> rwTest() async {
List<int> d = [65, 84, 13];
Uint8List bytes = Uint8List.fromList(d);
SerialPort port = SerialPort('COM115');
// configuration
final configu = SerialPortConfig();
configu.baudRate = 9600;
configu.bits = 8;
configu.parity = 0;
port.config = configu;
SerialPortReader reader = SerialPortReader(port, timeout: 10);
try {
port.openReadWrite();
print(port.write(bytes));
await reader.stream.listen((data) {
print('received : $data');
});
} on SerialPortError catch (_, err) {
if (port.isOpen) {
port.close();
print('serial port error');
}
}
}

Answer 2

The serial port need to open as far as the communication is active to send and receive data
Remove the port close method call
try {
port.openReadWrite();
print(port.write(bytes));
await reader.stream.listen((data) {
print('received : $data');
});
//port.close(); --> remove this line
}
On exit close the reader stream and then close the port