How to use Dart socket onError as inline function? - sockets

Question

I have dart socket that gets very long data. Lucky the third party add '\r\n' end of the data, so I can close when I find last data has '\r\n'.
In weeks I am trying to get long data due server problem. Before I used to waiting endlessly to server closes the connection (sometime took me 10 to 12 min)
Now seems everything works but a small problem. I used to get onError and onDone using void function. But I am using aqueduct so I need to return long data after I receive from server as a response.
In my below full code its keep printing "Server_Error". If I comment below data seems everything works. But my problem is that I need to return error data as well.
onError: () {
print("Server_Error");
},
onDone: () {
_socket.destroy();
},
cancelOnError: true);
If I comment above part I can print the long data.
My question is that, based on my scenario how to use Dart socket onError as inline function?
import 'dart:io';
import 'dart:convert';
import 'dart:typed_data';
Socket _socket;
String _reply;
String _testValue = "";
main() async {
String _queryA = “QueryLongData”;
await Socket.connect("192.168.22.120”, 3000).then((Socket sock) {
_socket = sock;
_socket.write('$_queryA\r\n');
_socket.listen((data) {
final List<int> byteArray = data;
_reply = String.fromCharCodes(byteArray);
int dataLen = _reply.length;
int carriageReturnPosition = dataLen - 2;
int newLinePosition = dataLen - 1;
_testValue = _testValue + _reply;
if (_reply.substring(carriageReturnPosition, newLinePosition) == '\r' &&
_reply.substring(newLinePosition, dataLen) == '\n') {
_socket.close();
print("Data: $_testValue"); // means return data
}
}, onError: () {
print("Server_Error");
},
onDone: () {
_socket.destroy();
},
cancelOnError: true);
}).catchError((e) {
print("Server_Error");
});
if(_socket.done == true) {
print("Exiting...");
exit(0);
}
}

Answer 1

<!-- language: dart -->
String _queryA = "QueryLongData";
Socket.connect("192.168.22.120", 3000).then((Socket sock) {
_socket = sock;
_socket.write("$_queryA\r\n");
_socket.listen((data) {
final List<int> byteArray = data;
_reply = String.fromCharCodes(byteArray);
int dataLen = _reply.length;
int carriageReturnPosition = dataLen - 2;
int newLinePosition = dataLen - 1;
_testValue = _testValue + _reply;
if (_reply.substring(carriageReturnPosition, newLinePosition) == "\r" &&
_reply.substring(newLinePosition, dataLen) == "\n") {
_socket.close();
print("Data: $_testValue"); // means return data
}
}, onError: () => print("Server_Error"),
onDone: () => _socket.destroy(),
cancelOnError: true);
}).catchError((e) => print("Server_Error"));
if( ( await _socket.done enter code here) == true) {
print("Exiting...");
exit(0);
}