Procedura: utilizzare le unnamed pipe per la comunicazione tra i processi locali
Le unnamed pipe offrono meno funzionalià rispetto alle named pipe ma richiedono meno overhead. È possibile utilizzarle per agevolare la comunicazione interprocesso su un computer locale. Non è possibile utilizzare le unnamed pipe per la comunicazione in una rete.
Esempio
Nell'esempio riportato di seguito viene illustrata una modalità per inviare una stringa da un processo padre a un processo figlio utilizzando le unnamed pipe. Viene creato un oggetto AnonymousPipeServerStream in un processo padre con un valore PipeDirection di Out. Il processo padre crea quindi un processo figlio utilizzando un handle del client per creare un oggetto AnonymousPipeClientStream. Il processo figlio ha un valore PipeDirection di In.
Il processo padre invia quindi una stringa fornita dall'utente al processo figlio. La stringa viene visualizzata nella console del processo figlio.
Nell'esempio riportato di seguito viene illustrato un processo server.
Imports System
Imports System.IO
Imports System.IO.Pipes
Imports System.Diagnostics
Class PipeServer
Shared Sub Main()
Dim pipeClient As New Process()
pipeClient.StartInfo.FileName = "pipeClient.exe"
Using pipeServer As New AnonymousPipeServerStream(PipeDirection.Out, _
HandleInheritability.Inheritable)
' Show that anonymous pipes do not support Message mode.
Try
Console.WriteLine("[SERVER] Setting ReadMode to ""Message"".")
pipeServer.ReadMode = PipeTransmissionMode.Message
Catch e As NotSupportedException
Console.WriteLine("[SERVER] Exception:\n {0}", e.Message)
End Try
Console.WriteLine("[SERVER] Current TransmissionMode: {0}.",
pipeServer.TransmissionMode)
' Pass the client process a handle to the server.
pipeClient.StartInfo.Arguments = pipeServer.GetClientHandleAsString()
pipeClient.StartInfo.UseShellExecute = false
pipeClient.Start()
pipeServer.DisposeLocalCopyOfClientHandle()
Try
' Read user input and send that to the client process.
Using sw As New StreamWriter(pipeServer)
sw.AutoFlush = true
' Send a 'sync message' and wait for client to receive it.
sw.WriteLine("SYNC")
pipeServer.WaitForPipeDrain()
' Send the console input to the client process.
Console.Write("[SERVER] Enter text: ")
sw.WriteLine(Console.ReadLine())
End Using
Catch e As IOException
' Catch the IOException that is raised if the pipe is broken
' or disconnected.
Console.WriteLine("[SERVER] Error: {0}", e.Message)
End Try
End Using
pipeClient.WaitForExit()
pipeClient.Close()
Console.WriteLine("[SERVER] Client quit. Server terminating.")
End Sub
End Class
using System;
using System.IO;
using System.IO.Pipes;
using System.Diagnostics;
class PipeServer
{
static void Main()
{
Process pipeClient = new Process();
pipeClient.StartInfo.FileName = "pipeClient.exe";
using (AnonymousPipeServerStream pipeServer =
new AnonymousPipeServerStream(PipeDirection.Out,
HandleInheritability.Inheritable))
{
// Show that anonymous pipes do not support Message mode.
try
{
Console.WriteLine("[SERVER] Setting ReadMode to \"Message\".");
pipeServer.ReadMode = PipeTransmissionMode.Message;
}
catch (NotSupportedException e)
{
Console.WriteLine("[SERVER] Exception:\n {0}", e.Message);
}
Console.WriteLine("[SERVER] Current TransmissionMode: {0}.",
pipeServer.TransmissionMode);
// Pass the client process a handle to the server.
pipeClient.StartInfo.Arguments =
pipeServer.GetClientHandleAsString();
pipeClient.StartInfo.UseShellExecute = false;
pipeClient.Start();
pipeServer.DisposeLocalCopyOfClientHandle();
try
{
// Read user input and send that to the client process.
using (StreamWriter sw = new StreamWriter(pipeServer))
{
sw.AutoFlush = true;
// Send a 'sync message' and wait for client to receive it.
sw.WriteLine("SYNC");
pipeServer.WaitForPipeDrain();
// Send the console input to the client process.
Console.Write("[SERVER] Enter text: ");
sw.WriteLine(Console.ReadLine());
}
}
// Catch the IOException that is raised if the pipe is broken
// or disconnected.
catch (IOException e)
{
Console.WriteLine("[SERVER] Error: {0}", e.Message);
}
}
pipeClient.WaitForExit();
pipeClient.Close();
Console.WriteLine("[SERVER] Client quit. Server terminating.");
}
}
#using <System.dll>
#using <System.Core.dll>
using namespace System;
using namespace System::IO;
using namespace System::IO::Pipes;
using namespace System::Diagnostics;
ref class PipeServer
{
public:
static void Main()
{
Process^ pipeClient = gcnew Process();
pipeClient->StartInfo->FileName = "pipeClient.exe";
AnonymousPipeServerStream^ pipeServer =
gcnew AnonymousPipeServerStream(PipeDirection::Out,
HandleInheritability::Inheritable);
// Show that anonymous pipes do not support Message mode.
try
{
Console::WriteLine("[SERVER] Setting ReadMode to \"Message\".");
pipeServer->ReadMode = PipeTransmissionMode::Message;
}
catch (NotSupportedException^ e)
{
Console::WriteLine("[SERVER] Exception:\n {0}", e->Message);
}
Console::WriteLine("[SERVER] Current TransmissionMode: {0}.",
pipeServer->TransmissionMode);
// Pass the client process a handle to the server.
pipeClient->StartInfo->Arguments =
pipeServer->GetClientHandleAsString();
pipeClient->StartInfo->UseShellExecute = false;
pipeClient->Start();
pipeServer->DisposeLocalCopyOfClientHandle();
try
{
// Read user input and send that to the client process.
StreamWriter^ sw = gcnew StreamWriter(pipeServer);
sw->AutoFlush = true;
// Send a 'sync message' and wait for client to receive it.
sw->WriteLine("SYNC");
pipeServer->WaitForPipeDrain();
// Send the console input to the client process.
Console::Write("[SERVER] Enter text: ");
sw->WriteLine(Console::ReadLine());
sw->Close();
}
// Catch the IOException that is raised if the pipe is broken
// or disconnected.
catch (IOException^ e)
{
Console::WriteLine("[SERVER] Error: {0}", e->Message);
}
pipeServer->Close();
pipeClient->WaitForExit();
pipeClient->Close();
Console::WriteLine("[SERVER] Client quit. Server terminating.");
}
};
int main()
{
PipeServer::Main();
}
Nell'esempio riportato di seguito viene illustrato un processo client. Il processo server avvia il processo client e lo passa all'handle del client. Il file eseguibile risultante dal codice client deve essere denominato pipeClient.exe e copiato alla stessa directory del file eseguibile del server prima di eseguire il processo server.
Imports System
Imports System.IO
Imports System.IO.Pipes
Class PipeClient
Shared Sub Main(args() as String)
If args.Length > 0 Then
Using pipeClient As New AnonymousPipeClientStream(PipeDirection.In, args(0))
' Show that anonymous Pipes do not support Message mode.
Try
Console.WriteLine("[CLIENT] Setting ReadMode to ""Message"".")
pipeClient.ReadMode = PipeTransmissionMode.Message
Catch e As NotSupportedException
Console.WriteLine("[CLIENT] Execption:" + vbNewLine + " {0}", e.Message)
End Try
Console.WriteLine("[CLIENT] Current TransmissionMode: {0}.", _
pipeClient.TransmissionMode)
Using sr As New StreamReader(pipeClient)
' Display the read text to the console
Dim temp As String
' Wait for 'sync message' from the server.
Do
Console.WriteLine("[CLIENT] Wait for sync...")
temp = sr.ReadLine()
Loop While temp.StartsWith("SYNC") = False
' Read the server data and echo to the console.
temp = sr.ReadLine()
While Not temp = Nothing
Console.WriteLine("[CLIENT] Echo: " + temp)
temp = sr.ReadLine()
End While
End Using
End Using
End If
Console.Write("[CLIENT] Press Enter to continue...")
Console.ReadLine()
End Sub
End Class
using System;
using System.IO;
using System.IO.Pipes;
class PipeClient
{
static void Main(string[] args)
{
if (args.Length > 0)
{
using (PipeStream pipeClient =
new AnonymousPipeClientStream(PipeDirection.In, args[0]))
{
// Show that anonymous Pipes do not support Message mode.
try
{
Console.WriteLine("[CLIENT] Setting ReadMode to \"Message\".");
pipeClient.ReadMode = PipeTransmissionMode.Message;
}
catch (NotSupportedException e)
{
Console.WriteLine("[CLIENT] Execption:\n {0}", e.Message);
}
Console.WriteLine("[CLIENT] Current TransmissionMode: {0}.",
pipeClient.TransmissionMode);
using (StreamReader sr = new StreamReader(pipeClient))
{
// Display the read text to the console
string temp;
// Wait for 'sync message' from the server.
do
{
Console.WriteLine("[CLIENT] Wait for sync...");
temp = sr.ReadLine();
}
while (!temp.StartsWith("SYNC"));
// Read the server data and echo to the console.
while ((temp = sr.ReadLine()) != null)
{
Console.WriteLine("[CLIENT] Echo: " + temp);
}
}
}
}
Console.Write("[CLIENT] Press Enter to continue...");
Console.ReadLine();
}
}
#using <System.Core.dll>
using namespace System;
using namespace System::IO;
using namespace System::IO::Pipes;
ref class PipeClient
{
public:
static void Main(array<String^>^ args)
{
if (args->Length > 1)
{
PipeStream^ pipeClient = gcnew AnonymousPipeClientStream(PipeDirection::In, args[1]);
// Show that anonymous Pipes do not support Message mode.
try
{
Console::WriteLine("[CLIENT] Setting ReadMode to \"Message\".");
pipeClient->ReadMode = PipeTransmissionMode::Message;
}
catch (NotSupportedException^ e)
{
Console::WriteLine("[CLIENT] Execption:\n {0}", e->Message);
}
Console::WriteLine("[CLIENT] Current TransmissionMode: {0}.",
pipeClient->TransmissionMode);
StreamReader^ sr = gcnew StreamReader(pipeClient);
// Display the read text to the console
String^ temp;
// Wait for 'sync message' from the server.
do
{
Console::WriteLine("[CLIENT] Wait for sync...");
temp = sr->ReadLine();
}
while (!temp->StartsWith("SYNC"));
// Read the server data and echo to the console.
while ((temp = sr->ReadLine()) != nullptr)
{
Console::WriteLine("[CLIENT] Echo: " + temp);
}
sr->Close();
pipeClient->Close();
}
Console::Write("[CLIENT] Press Enter to continue...");
Console::ReadLine();
}
};
int main()
{
array<String^>^ args = Environment::GetCommandLineArgs();
PipeClient::Main(args);
}
Vedere anche
Attività
Procedura: utilizzare le named pipe per la comunicazione tra processi in rete