C# NamedPipe 進程間通訊 (IPC) 完整實作：伺服器/用戶端雙向通訊

命名管道 是 Windows 高效能、安全、雙向的進程間通訊機制，支援跨機器 (SMB)、模擬、訊息/位元組模式。.NET 提供 NamedPipeServerStream/NamedPipeClientStream (System.IO.Pipes)，封裝底層 Win32 API。本文提供完整伺服器/用戶端雙向通訊範例，含非同步讀寫、連線生命週期、例外處理、多執行緒伺服器模式。

核心類別

1. 伺服器端 (Console App)

using System;
using System.IO.Pipes;
using System.Text;
using System.Threading.Tasks;

class PipeServer
{
    const string PipeName = "np-test-demo";
    static async Task Main()
    {
        Console.WriteLine($"啟動命名管道伺服器: {PipeName}");
        while (true) // 持續接受連線
        {
            using var server = new NamedPipeServerStream(
                PipeName, PipeDirection.InOut, 1, // max 1 instance for demo
                PipeTransmissionMode.Message, PipeOptions.Asynchronous);

            Console.WriteLine("等待用戶端連線...");
            await server.WaitForConnectionAsync();
            Console.WriteLine("用戶端已連線");

            try
            {
                // 讀取訊息 (Message 模式：一次讀一個完整訊息)
                var buffer = new byte[1024];
                int bytesRead = await server.ReadAsync(buffer, 0, buffer.Length);
                string request = Encoding.UTF8.GetString(buffer, 0, bytesRead);
                Console.WriteLine($"收到: {request}");

                // 回覆
                string response = $"Server Echo: {request}";
                byte[] respBytes = Encoding.UTF8.GetBytes(response);
                await server.WriteAsync(respBytes, 0, respBytes.Length);
                await server.FlushAsync();
                Console.WriteLine($"已回覆: {response}");

                if (request.Trim().Equals("exit", StringComparison.OrdinalIgnoreCase))
                    break;
            }
            catch (Exception ex)
            {
                Console.WriteLine($"通訊錯誤: {ex.Message}");
            }
            finally
            {
                server.Disconnect();
            }
        }
    }
}

2. 用戶端

using System;
using System.IO.Pipes;
using System.Text;
using System.Threading.Tasks;

class PipeClient
{
    const string PipeName = "np-test-demo";
    static async Task Main()
    {
        using var client = new NamedPipeClientStream(".", PipeName, PipeDirection.InOut, PipeOptions.Asynchronous);
        Console.WriteLine("連線至伺服器...");
        await client.ConnectAsync(5000); // 5 秒逾時
        Console.WriteLine("已連線");

        while (true)
        {
            Console.Write("輸入指令 (exit 結束): ");
            string input = Console.ReadLine();
            if (string.IsNullOrEmpty(input)) continue;

            byte[] req = Encoding.UTF8.GetBytes(input);
            await client.WriteAsync(req, 0, req.Length);
            await client.FlushAsync();

            var buffer = new byte[1024];
            int read = await client.ReadAsync(buffer, 0, buffer.Length);
            string resp = Encoding.UTF8.GetString(buffer, 0, read);
            Console.WriteLine($"伺服器回覆: {resp}");

            if (input.Equals("exit", StringComparison.OrdinalIgnoreCase)) break;
        }
    }
}

3. 進階：多執行緒伺服器 (同時處理多用戶端)

class ConcurrentPipeServer
{
    const string PipeName = "np-concurrent";
    static async Task Main()
    {
        var tasks = new List();
        for (int i = 0; i < Environment.ProcessorCount; i++)
        {
            tasks.Add(AcceptLoopAsync(i));
        }
        await Task.WhenAll(tasks);
    }

    static async Task AcceptLoopAsync(int instanceId)
    {
        while (true)
        {
            using var server = new NamedPipeServerStream(
                PipeName, PipeDirection.InOut, -1, // -1 = 不限實例數
                PipeTransmissionMode.Message, PipeOptions.Asynchronous);
            await server.WaitForConnectionAsync();
            _ = HandleClientAsync(server, instanceId); // Fire-and-forget
        }
    }

    static async Task HandleClientAsync(NamedPipeServerStream server, int id)
    {
        try
        {
            var buffer = new byte[4096];
            int read = await server.ReadAsync(buffer, 0, buffer.Length);
            string req = Encoding.UTF8.GetString(buffer, 0, read);
            string resp = $"Instance {id} Echo: {req}";
            byte[] data = Encoding.UTF8.GetBytes(resp);
            await server.WriteAsync(data, 0, data.Length);
            await server.FlushAsync();
        }
        catch { /* log */ }
        finally { server.Disconnect(); }
    }
}

關鍵細節與避坑

替代方案比較

結語

.NET System.IO.Pipes` 讓命名管道程式化極為簡單：建立 Stream、非同步讀寫、處理連線生命週期。掌握 Message 模式、Asynchronous 選項、多實例伺服器模式、安全性設定 即可構建穩健高效的 IPC 通道。跨平台專案請改用 gRPC 或 TCP；Windows 專有高效能場景，NamedPipe 為首選。