Android Socket Timeout Exception during Rest data connection, only during mobile network connection

  

After updating Delphi version 10.1 to 10.4.2, I encountered this problem, which only occurs on some Android 10 and 11 devices.
The APP exchanges data with the server via TDSRestConnection.
On the same phone, where previously the app developed with Delphi 10.1 worked correctly, stops working after the update to Delphi version 10.4.2 and after the Android upgrade on the phone.
The APP works only over the WiFi network and no longer works over the mobile network, generating this error after a while (7/8 seconds):

java.net.SocketTimeoutException: failed to connect to /xxx.xxx.xx.xx (port 17200) from /100.118.154.102 (port 42050) after 300000ms: isConnected failed: ETIMEDOUT (Connection timed out).

I also tried using different internet mobile providers (TIM, VODAFONE)
The 4G connection is Very Good and the Internet speed test doesn’t show any problem.
The error doesn’t appear immediately.
The function GetSql is called more times in the sincro procedure, but unfortunately it stops working not at the same point.
The code:
Client side:
const fConnectTimeout=300000;
const fReadTimeout=300000;

function TServerMethods1Client.GetSql(StringaSql: string; const ARequestFilter: string): TFDJSONDataSets;
begin
if FGetSqlCommand = nil then
begin
FGetSqlCommand := FConnection.CreateCommand;
FGetSqlCommand.RequestType := ‘GET’;
FGetSqlCommand.Text := ‘TServerMethods1.GetSql’;
FGetSqlCommand.Prepare(TServerMethods1_GetSql);
end;
FGetSqlCommand.Parameters[0].Value.SetWideString(StringaSql);
FGetSqlCommand.Execute(ARequestFilter);
if not FGetSqlCommand.Parameters[1].Value.IsNull then
begin
FUnMarshal := TDSRestCommand(FGetSqlCommand.Parameters[1].ConnectionHandler).GetJSONUnMarshaler;
try
Result := TFDJSONDataSets(FUnMarshal.UnMarshal(FGetSqlCommand.Parameters[1].Value.GetJSONValue(True)));
if FInstanceOwner then
FGetSqlCommand.FreeOnExecute(Result);
finally
FreeAndNil(FUnMarshal)
end
end
else
Result := nil;
end;

function SelectSql(StringaSQL:String;tb:TFDMemTable;out Errore:String):Boolean; overload;
var
jds: TFDJSONDataSets;
data: TFDAdaptedDataSet;
begin
try

result:=false;

if DMClientRestModule=nil then DMClientRestModule:=TDMClientRestModule.Create(nil);

DMClientRestModule.DSRestConnection1.Port := STRTOINT(REST_PORT);
DMClientRestModule.DSRestConnection1.Host := REST_HOST;
DMClientRestModule.DSRestConnection1.SessionID := ”;
DMClientRestModule.DSRestConnection1.HTTP.ConnectTimeout := fConnectTimeout;
DMClientRestModule.DSRestConnection1.HTTP.ReadTimeout := fReadTimeout;

jds :=TFDJSONDataSets.Create;

jds := DMClientRestModule.ServerMethods1Client.GetSql(StringaSql);
if (Assigned(jds)) then begin
data := TFDJSONDataSetsReader.GetListValue(jds, 0);
tb.AppendData(data);
tb.Open;
result:=true;
end;

try
DMClientRestModule.Free;
DMClientRestModule:=NIL;
except
end;

except
result:=false;
Errore:=GetStrException(ExceptObject,ExceptAddr);
end;

END;

Server side:
function TServerMethods1.GetSql(StringaSql: String): TFDJSONDataSets;
var
dset:TFDJSONDataSets;
begin

try

DbConn.Params.Clear; //TFDConnection
DbConn.Params.Database:=fdb;
DbConn.Params.UserName:=fuid;
DbConn.Params.Password:=fpwd;
DbConn.Params.Add(‘server=’+fdbserver);
DbConn.Params.Add(‘port=’+fport);
DbConn.Params.DriverID:=’MySQL’;

try
q1.Close; // TFDQuery

if not DbConn.Connected then
DbConn.Connected:=true;

if not DbConn.Connected then
log(‘Not conneted to db’)
else
log(‘Connected to db’) ;
with q1 do
begin
close;
SQL.Clear;
SQL.Add(StringaSql);
Log(StringaSQl);
open;
end;

Result := TFDJSONDataSets.Create;
// The "TFDJSONDataSetsWriter" class provides static "ListAdd" method.
// It uses reflection to convert results of the query into "TFDJSONDataSets".
TFDJSONDataSetsWriter.ListAdd(Result,”,q1);
except
Log(GetStrException(ExceptObject,ExceptAddr));
Result := TFDJSONDataSets.Create;
TFDJSONDataSetsWriter.ListAdd(Result,”,q1);
end;
finally
DbConn.Connected:=false;
end;

end;

update 16/04/2021
Investigating better, it seems that the Sql String that causes the exception is the following (Long text sql string)
StringaSql :=’SELECT PLANNING_ENGINEERS.DATE_JOB,NOT_A_JOB, ‘;
StringaSql := StringaSql + ‘ PLANNING.PLAN_ID,PLANNING.CONTACTID,PLANNING.CALLER_REFER, ‘;
StringaSql := StringaSql + ‘ PLANNING.COMPANYID,PLANNING.DEPOTID,CALLTYPEID,TIME_BEGIN,’;
StringaSql := StringaSql + ‘ TIME_END,LOCATION_DESCRIPTION,ADDRESS1,ADDRESS2,ZIP,PLACE,PROVINCE,’;
StringaSql := StringaSql + ‘ PHONE1,PHONE2,FAX,EMAIL,LATITUDE,LONGITUDE, ‘;
StringaSql := StringaSql + ‘ PLANNING.DELETED,PLANNING.CLOSED,PLANNING.SUSPENDED,PLANNING.NOTES,’;
StringaSql := StringaSql + ‘ PLANNING.INTERNAL_NOTES,PLANNING.SUGGESTION_NOTES,PLANNING.CLOSING_NOTES,ORDER_REFERENCE,EXTERNAL_REFERENCE, ‘;
StringaSql := StringaSql + ‘ EXTERNAL_REFERENCE_DESC ‘;
StringaSql := StringaSql + ‘ ,(SELECT CALLTYPES.DESCRIPTION FROM CALLTYPES WHERE CALLTYPES.CALLTYPE_ID=PLANNING.CALLTYPEID)’;
StringaSql := StringaSql + ‘ AS CALL_DESC ‘;
StringaSql := StringaSql + ‘ ,(SELECT CALLTYPES.TYPE FROM CALLTYPES WHERE CALLTYPES.CALLTYPE_ID=PLANNING.CALLTYPEID)’;
StringaSql := StringaSql + ‘ AS CALL_TYPE ‘;
StringaSql := StringaSql + ‘ ,(SELECT DEPOTS.NOTES FROM DEPOTS WHERE DEPOTS.DEPOT_ID=PLANNING.DEPOTID)’;
StringaSql := StringaSql + ‘ AS DEPOT_NOTES ‘;
StringaSql := StringaSql + ‘ FROM PLANNING,PLANNING_ENGINEERS WHERE ‘;
StringaSql := StringaSql + ‘ PLANNING.DELETED=”N” AND PLANNING.CLOSED=”N” AND PLANNING.SUSPENDED=”N” ‘;
StringaSql := StringaSql + ‘ AND PLANNING_ENGINEERS.PLANID=PLAN_ID ‘;
StringaSql := StringaSql + ‘ AND PLANNING_ENGINEERS.ENGINEERID=’+’42’;
StringaSql := StringaSql + ‘ AND PLANNING_ENGINEERS.DATE_JOB BETWEEN ‘+QuotedStr(FormatDateTime(‘YYYYMMDD’, date))+’ AND ‘+QuotedStr(FormatDateTime(‘YYYYMMDD’,date))+’ ‘;
StringaSql := StringaSql + ‘ ORDER BY DATE_JOB,TIME_BEGIN’;

During the WIFI connection, the call to the server works fine then it send back the result.
Instead during the 4G connection, the call raise the exception below:

Exception ENetHTTPClientException in module …
java.net.SocketException : Connection reset.

I also reported a ticket RSP-33699 to Embarcadero
Here the video: RestIssue

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