Enhance socket cleanup and management for improved connection handling

- Refactor cleanupSocket function to support options for immediate destruction, allowing drain, and grace periods.
- Introduce createIndependentSocketHandlers for better management of half-open connections between client and server sockets.
- Update various handlers (HTTP, HTTPS passthrough, HTTPS terminate) to utilize new cleanup and socket management functions.
- Implement custom timeout handling in socket setup to prevent immediate closure during keep-alive connections.
- Add tests for long-lived connections and half-open connection scenarios to ensure stability and reliability.
- Adjust connection manager to handle socket cleanup based on activity status, improving resource management.

test/test.long-lived-connections.ts

@@ -0,0 +1,192 @@
+import { tap, expect } from '@git.zone/tstest/tapbundle';
+import * as net from 'net';
+import * as tls from 'tls';
+import { SmartProxy } from '../ts/index.js';
+
+let testProxy: SmartProxy;
+let targetServer: net.Server;
+
+// Create a simple echo server as target
+tap.test('setup test environment', async () => {
+  // Create target server that echoes data back
+  targetServer = net.createServer((socket) => {
+    console.log('Target server: client connected');
+    
+    // Echo data back
+    socket.on('data', (data) => {
+      console.log(`Target server received: ${data.toString().trim()}`);
+      socket.write(data);
+    });
+    
+    socket.on('close', () => {
+      console.log('Target server: client disconnected');
+    });
+  });
+  
+  await new Promise<void>((resolve) => {
+    targetServer.listen(9876, () => {
+      console.log('Target server listening on port 9876');
+      resolve();
+    });
+  });
+  
+  // Create proxy with simple TCP forwarding (no TLS)
+  testProxy = new SmartProxy({
+    routes: [{
+      name: 'tcp-forward-test',
+      match: {
+        ports: 8888  // Plain TCP port
+      },
+      action: {
+        type: 'forward',
+        target: {
+          host: 'localhost',
+          port: 9876
+        }
+        // No TLS configuration - just plain TCP forwarding
+      }
+    }],
+    defaults: {
+      target: {
+        host: 'localhost',
+        port: 9876
+      }
+    },
+    enableDetailedLogging: true,
+    keepAliveTreatment: 'extended',  // Allow long-lived connections
+    inactivityTimeout: 3600000,      // 1 hour
+    socketTimeout: 3600000,          // 1 hour
+    keepAlive: true,
+    keepAliveInitialDelay: 1000
+  });
+  
+  await testProxy.start();
+});
+
+tap.test('should keep WebSocket-like connection open for extended period', async (tools) => {
+  tools.timeout(65000); // 65 second test timeout
+  
+  const client = new net.Socket();
+  let messagesReceived = 0;
+  let connectionClosed = false;
+  
+  // Connect to proxy
+  await new Promise<void>((resolve, reject) => {
+    client.connect(8888, 'localhost', () => {
+      console.log('Client connected to proxy');
+      resolve();
+    });
+    
+    client.on('error', reject);
+  });
+  
+  // Set up data handler
+  client.on('data', (data) => {
+    console.log(`Client received: ${data.toString().trim()}`);
+    messagesReceived++;
+  });
+  
+  client.on('close', () => {
+    console.log('Client connection closed');
+    connectionClosed = true;
+  });
+  
+  // Send initial handshake-like data
+  client.write('HELLO\n');
+  
+  // Wait for response
+  await new Promise(resolve => setTimeout(resolve, 100));
+  expect(messagesReceived).toEqual(1);
+  
+  // Simulate WebSocket-like keep-alive pattern
+  // Send periodic messages over 60 seconds
+  const startTime = Date.now();
+  const pingInterval = setInterval(() => {
+    if (!connectionClosed && Date.now() - startTime < 60000) {
+      console.log('Sending ping...');
+      client.write('PING\n');
+    } else {
+      clearInterval(pingInterval);
+    }
+  }, 10000); // Every 10 seconds
+  
+  // Wait for 61 seconds
+  await new Promise(resolve => setTimeout(resolve, 61000));
+  
+  // Clean up interval
+  clearInterval(pingInterval);
+  
+  // Connection should still be open
+  expect(connectionClosed).toEqual(false);
+  
+  // Should have received responses (1 hello + 6 pings)
+  expect(messagesReceived).toBeGreaterThan(5);
+  
+  // Close connection gracefully
+  client.end();
+  
+  // Wait for close
+  await new Promise(resolve => setTimeout(resolve, 100));
+  expect(connectionClosed).toEqual(true);
+});
+
+tap.test('should support half-open connections', async () => {
+  const client = new net.Socket();
+  const serverSocket = await new Promise<net.Socket>((resolve) => {
+    targetServer.once('connection', resolve);
+    client.connect(8888, 'localhost');
+  });
+  
+  let clientClosed = false;
+  let serverClosed = false;
+  let serverReceivedData = false;
+  
+  client.on('close', () => {
+    clientClosed = true;
+  });
+  
+  serverSocket.on('close', () => {
+    serverClosed = true;
+  });
+  
+  serverSocket.on('data', () => {
+    serverReceivedData = true;
+  });
+  
+  // Client sends data then closes write side
+  client.write('HALF-OPEN TEST\n');
+  client.end(); // Close write side only
+  
+  // Wait a bit
+  await new Promise(resolve => setTimeout(resolve, 500));
+  
+  // Server should still be able to send data
+  expect(serverClosed).toEqual(false);
+  serverSocket.write('RESPONSE\n');
+  
+  // Wait for data
+  await new Promise(resolve => setTimeout(resolve, 100));
+  
+  // Now close server side
+  serverSocket.end();
+  
+  // Wait for full close
+  await new Promise(resolve => setTimeout(resolve, 500));
+  
+  expect(clientClosed).toEqual(true);
+  expect(serverClosed).toEqual(true);
+  expect(serverReceivedData).toEqual(true);
+});
+
+tap.test('cleanup', async () => {
+  await testProxy.stop();
+  
+  await new Promise<void>((resolve) => {
+    targetServer.close(() => {
+      console.log('Target server closed');
+      resolve();
+    });
+  });
+});
+
+export default tap.start();