我正在尝试通过套接字连接向两台打印机发送打印指令。脚本工作正常，然后挂起并报告：
System.IO.IOException：无法将数据写入传输 连接：不允许发送或接收数据的请求，因为 插座已在该方向关闭，并带有 上一个关机调用
或
System.Net.Sockets.SocketException (0x80004005)： 连接尝试失败，因为连接的一方未正确响应 一段时间后，或建立的连接失败，因为 连接的主机无法响应
该问题是间歇性的，我无法在附加调试器的情况下重现。
任何人都可以发现可能导致这种行为的原因吗？我在线程安全方面遇到了问题，我认为这可能是罪魁祸首。
对代码量表示歉意。由于这可能归结为线程，我已经包含了尽可能多的范围。
// main entry point
class HomeController{
List<string> lsLabelResults = new List<string>("label result");
PrinterBench pbBench = new PrinterBench("192.168.2.20","192.168.2.21");
void Process(){
oPrintController = new PrintController(this);
if(GetLabel()){
// should always come out of the big printer (runs in background)
oPrintController.PrintBySocketThreaded(lsLabelResults, pbBench.PostageLabelIP);
// should always come out of the small printer
oPrintController.PrintWarningLabel();
}
}
}
class PrintController{
HomeController oHC;
private static Dictionary<string, Socket> lSocks = new Dictionary<string, Socket>();
private BackgroundWorker _backgroundWorker;
static readonly object locker = new object();
double dProgress;
bool bPrintSuccess = true;
public PrintController(HomeController oArg_HC)
{
oHC = oArg_HC;
}
public bool InitSocks()
{
// Ensure the IP's / endpoints of users printers are assigned
if (!lSocks.ContainsKey(oHC.pbBench.PostageLabelIP))
{
lSocks.Add(oHC.pbBench.PostageLabelIP, null);
}
if (!lSocks.ContainsKey(oHC.pbBench.SmallLabelIP))
{
lSocks.Add(oHC.pbBench.SmallLabelIP, null);
}
// attempt to create a connection to each socket
try
{
foreach (string sKey in lSocks.Keys.ToList())
{
if (lSocks[sKey] == null || !lSocks[sKey].Connected)
{
IPEndPoint ep = new IPEndPoint(IPAddress.Parse(sKey), 9100);
lSocks[sKey] = new Socket(ep.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
try
{
//lSocks[sKey].Connect(ep);
var result = lSocks[sKey].BeginConnect(ep, null, null);
bool success = result.AsyncWaitHandle.WaitOne(2000, true);
// dont need success
if (lSocks[sKey].Connected)
{
lSocks[sKey].EndConnect(result);
}
else
{
lSocks[sKey].Close();
throw new SocketException(10060); // Connection timed out.
}
}
catch(SocketException se)
{
if(se.ErrorCode == 10060)
{
oHC.WriteLog("Unable to init connection to printer. Is it plugged in?", Color.Red);
}
else
{
oHC.WriteLog("Unable to init connection to printer. Error: " + se.ErrorCode.ToString(), Color.Red);
}
}
catch (Exception e)
{
oHC.WriteLog("Unable to init connection to printer. Error: " + e.ToString(), Color.Red);
}
}
}
}catch (Exception e)
{
oHC.WriteLog(e.ToString(), true);
return false;
}
return true;
}
public bool PrintBySocketThreaded(List<string> lsToPrint, string sIP)
{
// open both the sockets
InitSocks();
bBatchPrintSuccess = false;
_backgroundWorker = new BackgroundWorker();
_backgroundWorker.DoWork += new DoWorkEventHandler(backgroundWorker_DoWork);
_backgroundWorker.RunWorkerCompleted += backgroundWorker_RunWorkerCompleted;
_backgroundWorker.WorkerReportsProgress = true;
_backgroundWorker.WorkerSupportsCancellation = true;
object[] parameters = new object[] { lsToPrint, sIP, lSocks };
_backgroundWorker.RunWorkerAsync(parameters);
return true;
}
// On worker thread, send to print!
public void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
object[] parameters = e.Argument as object[];
double dProgressChunks = (100 / ((List<string>)parameters[0]).Count);
int iPos = 1;
Dictionary<string, Socket> dctSocks = (Dictionary<string, Socket>)parameters[2];
foreach (string sLabel in (List<string>)parameters[0] )
{
bool bPrinted = false;
// thread lock print by socket to ensure its not accessed twice
lock (locker)
{
// get relevant socket from main thread
bPrinted = PrintBySocket(sLabel, (string)parameters[1], dctSocks[(string)parameters[1]]);
}
iPos++;
}
while (!((BackgroundWorker)sender).CancellationPending)
{
((BackgroundWorker)sender).CancelAsync();
((BackgroundWorker)sender).Dispose();
//Thread.Sleep(500);
}
return;
}
// Back on the 'UI' thread so we can update the progress bar (have access to main thread data)!
private void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Error != null) MessageBox.Show(e.Error.Message);
if (bPrintSuccess) oHC.WriteLog("Printing Complete");
bBatchPrintSuccess = true;
((BackgroundWorker)sender).CancelAsync();
((BackgroundWorker)sender).Dispose();
}
/// sends to printer via socket
public bool PrintBySocket(string sArg_ToPrint, string sIP, Socket sock = null)
{
Socket sTmpSock = sock;
if (sTmpSock == null)
{
InitSocks();
if (!lSocks.ContainsKey(sIP))
{
throw new Exception("Sock not init");
}
else
{
sTmpSock = lSocks[sIP];
}
}
try
{
if(!sTmpSock.Connected || !sTmpSock.IsBound)
{
InitSocks();
if (!sTmpSock.Connected)
{
oHC.WriteLog("Unable to init connection to printer. Is it plugged in?", Color.Red);
}
}
using (NetworkStream ns = new NetworkStream(sTmpSock))
{
byte[] toSend = null;
// convert string to byte stream, or use byte stream
if (byToPrint == null)
{
toSend = Encoding.ASCII.GetBytes(sEOL + sArg_ToPrint);
}
else
{
toSend = byToPrint;
}
ns.BeginWrite(toSend, 0, toSend.Length, OnWriteComplete, null);
ns.Flush();
}
return true;
}
catch (Exception e)
{
oHC.WriteLog("Print by socket: " + e.ToString(), true);
DisposeSocks();
}
}
public bool PrintWarningLabel()
{
string sOut = sEOL + "N" + sEOL;
sOut += "A0,150,0,4,3,3,N,"WARNING MESSAGE TO PRINT"" + sEOL;
sOut += sEOL;
if (PrintBySocket(sOut, oHC.pbBench.SmallLabelIP))
{
oHC.WriteLog("WARNING LABEL PRINTED");
return true;
}
return false;
}
}
您似乎正在连接到TCP服务器并发送一些数据。在现代 .NET 中，您不需要显式多线程，异步等待大大简化了事情。以下是我可能会这样做的方法。
static class NetworkPrinter
{
const ushort tcpPort = 31337;
const string sEOL = "rn";
/// <summary>Send a single job to the printer.</summary>
static async Task sendLabel( Stream stream, string what, CancellationToken ct )
{
byte[] toSend = Encoding.ASCII.GetBytes( sEOL + what );
await stream.WriteAsync( toSend, 0, toSend.Length, ct );
await stream.FlushAsync();
}
/// <summary>Connect to a network printer, send a batch of jobs reporting progress, disconnect.</summary>
public static async Task printLabels( string ip, string[] labels, Action<double> progress, CancellationToken ct )
{
IPAddress address = IPAddress.Parse( ip );
double progressMul = 1.0 / labels.Length;
using( var tc = new TcpClient() )
{
await tc.ConnectAsync( address, tcpPort );
Stream stream = tc.GetStream();
for( int i = 0; i < labels.Length; )
{
ct.ThrowIfCancellationRequested();
await sendLabel( stream, labels[ i ], ct );
i++;
progress( i * progressMul );
}
}
}
/// <summary>Send multiple batches to multiple printers, return true of all of them were good.</summary>
public static async Task<bool> printBatches( LabelBatch[] batches )
{
await Task.WhenAll( batches.Select( a => a.print( CancellationToken.None ) ) );
return batches.All( a => a.completed );
}
}
/// <summary>A batch of labels to be printed by a single printer.</summary>
/// <remarks>Once printed, includes some status info.</remarks>
class LabelBatch
{
readonly string ip;
readonly string[] labels;
public bool completed { get; private set; } = false;
public Exception exception { get; private set; } = null;
public LabelBatch( string ip, IEnumerable<string> labels )
{
this.ip = ip;
this.labels = labels.ToArray();
}
/// <summary>Print all labels, ignoring the progress. This method doesn't throw, returns false if failed.</summary>
public async Task<bool> print( CancellationToken ct )
{
completed = false;
exception = null;
try
{
await NetworkPrinter.printLabels( ip, labels, d => { }, ct );
completed = true;
}
catch( Exception ex )
{
exception = ex;
}
return completed;
}
}
如果没有同步上下文(例如，您正在编写控制台应用)来报告进度，则可能仍需要手动线程同步。您可以获取从多台打印机并行调用的进度回调。进度报告应该很快，静态对象上的单个 lock() 就可以了。如果您正在构建 GUI 应用程序并从 GUI 线程调用 printBatches，则不需要，sync.context 会将所有内容序列化到 GUI 线程，尽管网络请求仍将并行运行。