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Improve TCP connect timeout handling in ModbusTcpClient #158

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Improve TCP connect timeout handling in ModbusTcpClient #158

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15 changes: 13 additions & 2 deletions src/FluentModbus/Client/ModbusTcpClient.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -167,8 +167,19 @@ private void Initialize(TcpClient tcpClient, IPEndPoint? remoteEndpoint, ModbusE
var isInternal = remoteEndpoint is not null;
_tcpClient = (tcpClient, isInternal);

if (remoteEndpoint is not null && !tcpClient.ConnectAsync(remoteEndpoint.Address, remoteEndpoint.Port).Wait(ConnectTimeout))
throw new Exception(ErrorMessage.ModbusClient_TcpConnectTimeout);
if (remoteEndpoint is not null)
{
var connectTask = tcpClient.ConnectAsync(remoteEndpoint.Address, remoteEndpoint.Port);
if (!connectTask.Wait(ConnectTimeout))
{
// Ensure the task exception is observed to avoid triggering UnobservedTaskException handlers (which can crash the process or flood logs).
// Attaching a continuation that accesses task.Exception guarantees the exception is observed.
connectTask.ContinueWith(t => t.Exception, TaskContinuationOptions.OnlyOnFaulted | TaskContinuationOptions.ExecuteSynchronously);
// Close the TcpClient to cancel the connection attempt.
tcpClient.Close();
throw new Exception(ErrorMessage.ModbusClient_TcpConnectTimeout);
}
}

// Why no method signature with NetworkStream only and then set the timeouts
// in the Connect method like for the RTU client?
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