[英]Xamarin.Forms (Android) Bluetooth intermittently working
场景:
我正在使用Xamarin.Forms构建一个Android应用程序,该应用程序将部署到一组设备上。 除其中一个设备外,所有设备都将进行一些数据收集,而其余设备将成为“枢纽”,以聚合所有数据并进行一些报告。 我正在使用Bluetooth进行设备到设备的通信。 标有“主”的“集线器”充当客户端,所有收集器充当服务器。 我有一个原型,几乎可以使用一个服务器和一个客户端。
有时,客户端/主服务器将无法从服务器/收集器读取。 我正在努力寻找造成这种情况的原因,并希望得到任何帮助。
症状:
即使服务器已写入输出流,客户端从InputStream对.Read()的调用有时也会无限期地阻塞。 我在此呼叫中添加了超时,以防止应用程序完全卡住。 这是间歇性发生的,但是我发现了何时可以工作以及何时不能工作的模式
码:
所有蓝牙处理都由我使用Xamarin.Forms DependencyService注入的单个类/服务完成。 所有设备在启动时(通过此类的构造函数)将在后台线程上无限期地循环,等待连接并重复。 大部分蓝牙代码基于蓝牙聊天示例,以及我发现的其他一些在线资源(一些android native / java,一些Xamarin / C#)
主设备将按需(通过按UI中的按钮触发)尝试连接到任何收集器(通过绑定的蓝牙设备)并从中读取数据。 还有一个简单的UI组件,该组件实际上充当控制台日志。
这是整个服务类。
public class GameDataSyncService : IGameDataSyncService
{
private const string UUID = "8e99f5f1-4a07-4268-9686-3a288326e0a2";
private static Task acceptLoopTask;
private static Task syncDataTask;
private static readonly object locker = new object();
private static bool running = false;
public event EventHandler<DataSyncMessage> MessageBroadcast;
public GameDataSyncService()
{
// Every device will listen and accept incoming connections. The master will make the connections.
lock (locker)
{
if (acceptLoopTask == null)
{
acceptLoopTask = Task.Factory.StartNew(AcceptLoopWorker, TaskCreationOptions.LongRunning);
}
}
}
public void SyncData()
{
lock (locker)
{
if (running)
{
BroadcastMessage("Previous data sync is still running.", DataSyncMessageType.Warning);
return;
}
else
{
running = true;
syncDataTask = Task.Factory.StartNew(SyncDataWorker);
}
}
}
private void BroadcastMessage(string message, DataSyncMessageType type = DataSyncMessageType.Info)
{
MessageBroadcast?.Invoke(this, new DataSyncMessage { Text = message, Type = type });
}
private async Task AcceptLoopWorker()
{
int count = 0;
while (true)
{
BluetoothServerSocket serverSocket = null;
BluetoothSocket clientSocket = null;
try
{
BroadcastMessage($"Listening for incoming connection...", DataSyncMessageType.Debug);
serverSocket = BluetoothAdapter.DefaultAdapter.ListenUsingRfcommWithServiceRecord(nameof(GameDataSyncService), Java.Util.UUID.FromString(UUID));
clientSocket = serverSocket.Accept(); // This call blocks until a connection is established.
BroadcastMessage($"Connection received from {clientSocket.RemoteDevice.Name}. Sending data...", DataSyncMessageType.Info);
var bytes = Encoding.UTF8.GetBytes($"Hello World - {string.Join(" ", Enumerable.Repeat(Guid.NewGuid(), ++count))}");
await clientSocket.OutputStream.WriteAsync(bytes, 0, bytes.Length);
clientSocket.OutputStream.Flush();
// Give the master some time to close the connection from their end
await Task.Delay(1000*3);
}
catch (Exception ex)
{
BroadcastMessage($"{ex.GetType().FullName}: {ex.Message}", DataSyncMessageType.Debug);
}
finally
{
try { clientSocket?.InputStream?.Close(); } catch { }
try { clientSocket?.InputStream?.Dispose(); } catch { }
try { clientSocket?.OutputStream?.Close(); } catch { }
try { clientSocket?.OutputStream?.Dispose(); } catch { }
try { clientSocket?.Close(); } catch { }
try { clientSocket?.Dispose(); } catch { }
try { serverSocket?.Close(); } catch { }
try { serverSocket?.Dispose(); } catch { }
BroadcastMessage($"Connection closed.", DataSyncMessageType.Debug);
}
}
}
private async Task SyncDataWorker()
{
BroadcastMessage($"Beginning data sync...");
foreach (var bondedDevice in BluetoothAdapter.DefaultAdapter.BondedDevices.OrderBy(d => d.Name))
{
BluetoothSocket clientSocket = null;
try
{
clientSocket = bondedDevice.CreateRfcommSocketToServiceRecord(Java.Util.UUID.FromString(UUID));
BroadcastMessage($"Connecting to {bondedDevice.Name}...");
try
{
clientSocket.Connect();
}
catch
{
BroadcastMessage($"Connection to {bondedDevice.Name} failed.", DataSyncMessageType.Error);
}
while (clientSocket.IsConnected)
{
byte[] buffer = new byte[1024];
var readTask = clientSocket.InputStream.ReadAsync(buffer, 0, buffer.Length);
if (await Task.WhenAny(readTask, Task.Delay(1000)) != readTask)
{
BroadcastMessage($"Read timeout...", DataSyncMessageType.Error);
break;
}
int bytes = readTask.Result;
BroadcastMessage($"Read {bytes} bytes.", DataSyncMessageType.Success);
if (bytes > 0)
{
var text = Encoding.UTF8.GetString(buffer.Take(bytes).ToArray());
BroadcastMessage(text, DataSyncMessageType.Success);
break;
}
}
}
catch (Exception ex)
{
BroadcastMessage($"{ex.GetType().FullName}: {ex.Message}", DataSyncMessageType.Debug);
}
finally
{
try { clientSocket?.InputStream?.Close(); } catch { }
try { clientSocket?.InputStream?.Dispose(); } catch { }
try { clientSocket?.OutputStream?.Close(); } catch { }
try { clientSocket?.OutputStream?.Dispose(); } catch { }
try { clientSocket?.Close(); } catch { }
try { clientSocket?.Dispose(); } catch { }
}
}
await Task.Delay(1000 * 3);
BroadcastMessage($"Data sync complete!");
lock (locker)
{
running = false;
}
}
}
我尝试过的方法(下面没有任何效果):
其中大多数来自其他stackoverflow帖子中的“解决方案”。
视频:
我拍了一段视频。 后面的平板电脑是收集器/服务器。前台的平板电脑是主机/客户端。 视频开始播放时,客户端将显示以前的尝试,并且服务器应用程序处于后台(但正在运行)。 我演示了.Read在收集器/服务器应用程序在后台而不在前台的情况下有效。 每个开始数据同步的请求都有一个对应的“控制台”条目(如果我按得太早,则显示警告) https://youtu.be/NGuGa7upCU4
摘要:
据我所知,我的代码是正确的。 我不知道还有什么要更改/修复以更可靠地工作。 实际的连接似乎已成功(基于服务器/收集器的日志,不幸的是,未在视频中显示),但问题出在.Write(或.Read)中。 任何帮助,建议或见解都会很棒。
尝试以下操作,将其全部更改为使用:
private async Task AcceptLoopWorker()
{
int count = 0;
while (true)
{
try
{
BroadcastMessage("Listening for incoming connection...", DataSyncMessageType.Debug);
using (var serverSocket = BluetoothAdapter.DefaultAdapter.ListenUsingRfcommWithServiceRecord(nameof(GameDataSyncService), Java.Util.UUID.FromString(UUID)))
using (var clientSocket = serverSocket.Accept()) // This call blocks until a connection is established.
{
BroadcastMessage(string.Format("Connection received from {0}. Sending data...", clientSocket.RemoteDevice.Name), DataSyncMessageType.Info);
var bytes = System.Text.Encoding.UTF8.GetBytes(string.Format("Hello World - {0}", string.Join(" ", Enumerable.Repeat(Guid.NewGuid(), ++count))));
await clientSocket.OutputStream.WriteAsync(bytes, 0, bytes.Length);
}
await Task.Delay(1000 * 3); // Give the master some time to close the connection from their end
}
catch (Java.IO.IOException ex)
{
BroadcastMessage(string.Format("IOException {0}: {1}", ex.GetType().FullName, ex.Message), DataSyncMessageType.Debug);
}
catch (Java.Lang.Exception ex)
{
BroadcastMessage(string.Format("Exception {0}: {1}", ex.GetType().FullName, ex.Message), DataSyncMessageType.Debug);
}
}
}
private async Task SyncDataWorker()
{
BroadcastMessage("Beginning data sync...");
foreach (var bondedDevice in BluetoothAdapter.DefaultAdapter.BondedDevices.OrderBy(d => d.Name))
{
try
{
using (var clientSocket = bondedDevice.CreateRfcommSocketToServiceRecord(Java.Util.UUID.FromString(UUID)))
{
BroadcastMessage(string.Format("Connecting to {0}...", bondedDevice.Name));
if (!clientSocket.IsConnected)
{
clientSocket.Connect();
}
if (clientSocket.IsConnected)
{
byte[] buffer = new byte[1024];
var readTask = clientSocket.InputStream.ReadAsync(buffer, 0, buffer.Length);
if (await Task.WhenAny(readTask, Task.Delay(1000)) != readTask)
{
BroadcastMessage("Read timeout...", DataSyncMessageType.Error);
break;
}
int bytes = readTask.Result;
BroadcastMessage(string.Format("Read {0} bytes.", bytes), DataSyncMessageType.Success);
if (bytes > 0)
{
var text = System.Text.Encoding.UTF8.GetString(buffer.Take(bytes).ToArray());
BroadcastMessage(text, DataSyncMessageType.Success);
break;
}
}
else
{
BroadcastMessage("Not Connected...", DataSyncMessageType.Error);
}
}
}
catch (Java.IO.IOException ex)
{
BroadcastMessage(string.Format("IOException {0}: {1}", ex.GetType().FullName, ex.Message), DataSyncMessageType.Debug);
}
catch (Java.Lang.Exception ex)
{
BroadcastMessage(string.Format("Exception {0}: {1}", ex.GetType().FullName, ex.Message), DataSyncMessageType.Debug);
}
}
await Task.Delay(1000 * 3);
BroadcastMessage("Data sync complete!");
lock (locker)
{
running = false;
}
}
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