C# 为什么我的套接字输入流会丢失字节?
我正在创建一个基于套接字的系统,用于桌面和移动设备之间的通信。我使用一个简单的协议来读取和写入设备之间的数据流,这些数据最终以字节的形式结束:C# 为什么我的套接字输入流会丢失字节?,c#,sockets,stream,uwp,bytestream,C#,Sockets,Stream,Uwp,Bytestream,我正在创建一个基于套接字的系统,用于桌面和移动设备之间的通信。我使用一个简单的协议来读取和写入设备之间的数据流,这些数据最终以字节的形式结束: 前4个字节表示一个整数,它定义了要执行的命令类型 接下来的4个字节表示一个整数,它是流中其余字节的长度 剩余字节表示有效负载数据,其总数对应于(2)的结果 我能够成功剥离前4个字节并解析命令ok,然后剥离下4个字节并正确解析长度。 当我去掉剩余的字节时,问题就出现了,其中一些字节丢失了,并且它们从剩余数据的前面丢失了 比如,;如果命令是1,长度是50,那
- 命令:1
- 长度:50
- 有效载荷:C:\Users\dave\Music\Offaiah-troub\uu(Club\umix).mp3
IBuffer inbuffer = new Windows.Storage.Streams.Buffer(4);
await _socket.InputStream.ReadAsync(inbuffer, 4, InputStreamOptions.None);
int command = BitConverter.ToInt32(inbuffer.ToArray(), 0);
此时的inbuffer包含:“\u0001\0\0\0”,位转换器将其解析为1
inbuffer = new Windows.Storage.Streams.Buffer(4);
await _socket.InputStream.ReadAsync(inbuffer, 4, InputStreamOptions.None);
int length = BitConverter.ToInt32(inbuffer.ToArray(), 0);
inbuffer现在包含:“2\0\0\0”,位转换器将其解析为“50”
inbuffer现在包含:“sers\dave\Music\Offaiah-troub\u(Club\u Mix).mp3”
前面缺少的“C:\U”是从哪里来的?因此,我意识到我一直在投票,因为这个问题不简洁,不可重复。所以我创建了一个小项目来演示问题的这一部分,讽刺的是,问题消失了 代码如下:
public sealed partial class MainPage : Page
{
private StreamSocketListener _listener;
private StreamSocket _client;
private StreamSocket _socket;
private HostName _host;
private int _port = 54321;
public MainPage()
{
InitializeComponent();
_listener = new StreamSocketListener();
_listener.ConnectionReceived += async (sender, args) =>
{
_socket = args.Socket;
await Receive();
};
_host = NetworkInformation.GetHostNames().FirstOrDefault(x => x.IPInformation != null && x.Type == HostNameType.Ipv4);
}
protected async override void OnNavigatedTo(NavigationEventArgs e)
{
base.OnNavigatedTo(e);
await _listener.BindEndpointAsync(_host, $"{_port}");
await Task.Run(async () =>
{
_client = new StreamSocket();
await _client.ConnectAsync(_host, $"{_port}");
int command = 1;
byte[] cmd = BitConverter.GetBytes(command);
byte[] path = Encoding.UTF8.GetBytes(@"C:\Users\Dave\Music\Offaiah-Trouble_(Club_Mix).mp3");
byte[] length = BitConverter.GetBytes(path.Length);
byte[] result = cmd.Concat(length.Concat(path)).ToArray();
await _client.OutputStream.WriteAsync(result.AsBuffer());
});
}
private async Task Receive()
{
while (true)
{
IBuffer inbuffer = new Windows.Storage.Streams.Buffer(4);
await _socket.InputStream.ReadAsync(inbuffer, 4, InputStreamOptions.None);
int command = BitConverter.ToInt32(inbuffer.ToArray(), 0);
//The inbuffer at this point contains: "\u0001\0\0\0", and the BitConverter resolves this to 1
inbuffer = new Windows.Storage.Streams.Buffer(4);
await _socket.InputStream.ReadAsync(inbuffer, 4, InputStreamOptions.None);
int length = BitConverter.ToInt32(inbuffer.ToArray(), 0);
//The inbuffer now contains: "2\0\0\0", and the BitConverter resolves this to "50"
inbuffer = new Windows.Storage.Streams.Buffer((uint)length);
await _socket.InputStream.ReadAsync(inbuffer, (uint)length, InputStreamOptions.Partial);
string path = Encoding.UTF8.GetString(inbuffer.ToArray());
}
}
}
如果您创建一个新的空白通用项目并运行它,您将看到它生成了正确的输出
最终我发现我在这个流阅读器和另一个流阅读器之间有竞争条件。在主项目中,我不会一次性读取所有字节。在将控制权传递给另一个方法之前,我有一个单独的方法来读取和解析“命令”,将控制权重定向到几个辅助方法中的一个,以服务于特定的命令-剥离长度,然后剥离剩余的有效负载
问题是,“命令读取器”随后从流中读取了另外4个字节,然后工作程序才能读取其有效负载
很明显,答案是它应该在这里暂停并等待worker完成,但我使用的是async并在整个过程中等待,所以我很惊讶我遇到了这个问题。原因是缺少等待和可怕的异步无效,如下所示
违规代码:
private async Task Listen()
{
while (true)
{
//expects a 4 byte packet representing a command
Debug.WriteLine($"Listening for socket command...");
IBuffer inbuffer = new Windows.Storage.Streams.Buffer(4);
await _socket.InputStream.ReadAsync(inbuffer, 4, InputStreamOptions.None);
int command = BitConverter.ToInt32(inbuffer.ToArray(), 0);
Debug.WriteLine($"Command received: {command}");
ParseCommand(command);
}
}
private async void ParseCommand(int command)
{
//...
}
…以及最新版本:
private async Task Listen()
{
while (true)
{
//expects a 4 byte packet representing a command
Debug.WriteLine($"Listening for socket command...");
IBuffer inbuffer = new Windows.Storage.Streams.Buffer(4);
await _socket.InputStream.ReadAsync(inbuffer, 4, InputStreamOptions.None);
int command = BitConverter.ToInt32(inbuffer.ToArray(), 0);
Debug.WriteLine($"Command received: {command}");
await ParseCommand(command);
}
}
private async Task ParseCommand(int command)
{
//...
}
private async Task Listen()
{
while (true)
{
//expects a 4 byte packet representing a command
Debug.WriteLine($"Listening for socket command...");
IBuffer inbuffer = new Windows.Storage.Streams.Buffer(4);
await _socket.InputStream.ReadAsync(inbuffer, 4, InputStreamOptions.None);
int command = BitConverter.ToInt32(inbuffer.ToArray(), 0);
Debug.WriteLine($"Command received: {command}");
await ParseCommand(command);
}
}
private async Task ParseCommand(int command)
{
//...
}