max-connection-limit implemented

examples/tcp-proxy/build.gradle

@@ -3,6 +3,9 @@ plugins {
     id 'application'
 }
 
+sourceCompatibility = JavaVersion.VERSION_17
+targetCompatibility = JavaVersion.VERSION_17
+
 group = 'one.microproject.tcp.server'
 version = '1.0.0'
 mainClassName = 'one.microproject.tcp.server.Main'
@@ -14,4 +17,4 @@ dependencies {
     implementation 'com.fasterxml.jackson.core:jackson-core:2.13.0'
     implementation 'com.fasterxml.jackson.core:jackson-databind:2.13.0'
     implementation 'com.fasterxml.jackson.core:jackson-annotations:2.13.0'
-}
+}

examples/tcp-proxy/scripts/tcp-proxy-start.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+export JAVA_HOME=/opt/tcp-proxy/jdk1.8.0_251
+export PATH=$JAAVA_HOME/bin:$PATH
+
+LOG_FILE=/opt/tcp-proxy/tcp-proxy.log
+CONFIG=/opt/tcp-proxy/tcp-proxy-config.json
+
+mv $LOG_FILE $LOG_FILE.old
+
+/opt/tcp-proxy/tcp-proxy-1.0.0/bin/tcp-proxy $CONFIG > $LOG_FILE 2>&1
+

examples/tcp-proxy/scripts/tcp-proxy-stop.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+killall java

examples/tcp-proxy/scripts/tcp-proxy.service

@@ -0,0 +1,20 @@
+[Unit]
+Description=TCP Proxy Service
+After=network.target
+After=systemd-user-sessions.service
+After=network-online.target
+
+[Service]
+User=pi
+Type=simple
+WorkingDirectory=/opt/tcp-proxy
+ExecStart=/opt/tcp-proxy/tcp-proxy-start.sh
+ExecStop=/opt/tcp-proxy/tcp-proxy-stop.sh
+TimeoutSec=30
+Restart=on-failure
+RestartSec=30
+StartLimitInterval=350
+StartLimitBurst=10
+
+[Install]
+WantedBy=multi-user.target

examples/tcp-proxy/src/main/java/one/microproject/tcp/server/Main.java

@@ -23,7 +23,7 @@ public static void main(String[] args) throws IOException {
         Configuration configuration = mapper.readValue(new File(args[0]), Configuration.class);
         LOG.info("Starting TCP Proxy id={} name={} proxies={}", configuration.id(), configuration.name(), configuration.proxies().size());
         configuration.proxies().forEach(c -> {
-            LOG.info("Proxy Config: {}:{} -> {}:{}", c.serverHost(), c.serverPort(), c.targetHost(), c.targetPort());
+            LOG.info("Proxy Config: {}:{} -> {}:{} maxConnections={}", c.serverHost(), c.serverPort(), c.targetHost(), c.targetPort(), c.maxConnections());
             TCPProxyImpl tcpProxy = new TCPProxyImpl(c);
             try {
                 tcpProxy.start();

examples/tcp-proxy/src/main/java/one/microproject/tcp/server/impl/ConnectionRegistry.java

@@ -4,6 +4,8 @@ public interface ConnectionRegistry {
 
     void register(ActiveConnection activeConnection);
 
+    int getActiveConnections();
+
     void unregister(String id);
 
 }

examples/tcp-proxy/src/main/java/one/microproject/tcp/server/impl/ProxyConfiguration.java

@@ -1,4 +1,4 @@
 package one.microproject.tcp.server.impl;
 
-public record ProxyConfiguration(String serverHost, Integer serverPort, String targetHost, Integer targetPort) {
+public record ProxyConfiguration(String serverHost, Integer serverPort, String targetHost, Integer targetPort, Integer maxConnections) {
 }

examples/tcp-proxy/src/main/java/one/microproject/tcp/server/impl/TCPProxyImpl.java

@@ -21,6 +21,7 @@ public class TCPProxyImpl implements TcpProxy, ConnectionRegistry {
     private final Integer serverPort;
     private final String targetHost;
     private final Integer targetPort;
+    private final Integer maxConnections;
     private final Map<String, ActiveConnection> activeConnections;
 
     private TcpMain tcpMain;
@@ -31,17 +32,21 @@ public TCPProxyImpl(ProxyConfiguration configuration) {
         this.serverPort = configuration.serverPort();
         this.targetHost = configuration.targetHost();
         this.targetPort = configuration.targetPort();
+        this.maxConnections = configuration.maxConnections();
         this.activeConnections = new ConcurrentHashMap<>();
     }
 
     @Override
     public void start() throws IOException {
         LOG.info("Starting TCP proxy ...");
-        this.processors = Executors.newFixedThreadPool(8);
-        ServerSocket serverSocket = new ServerSocket(serverPort, 10, InetAddress.getByName(serverHost));
-        this.tcpMain = new TcpMain(this, serverSocket, processors, targetHost, targetPort);
-        processors.submit(tcpMain);
-        LOG.info("TCP proxy started.");
+        int threadPoolSize = 1 + (maxConnections*2);
+        LOG.info("Starting internal threadpool size={}", threadPoolSize);
+        this.processors = Executors.newFixedThreadPool(threadPoolSize);
+        try (ServerSocket serverSocket = new ServerSocket(serverPort, maxConnections, InetAddress.getByName(serverHost))) {
+            this.tcpMain = new TcpMain(this, serverSocket, processors, targetHost, targetPort, maxConnections);
+            processors.submit(tcpMain);
+            LOG.info("TCP proxy started.");
+        }
     }
 
     @Override
@@ -66,6 +71,11 @@ public synchronized void register(ActiveConnection activeConnection) {
         LOG.info("Active connections: {}", activeConnections.size());
     }
 
+    @Override
+    public synchronized int getActiveConnections() {
+        return activeConnections.size();
+    }
+
     @Override
     public synchronized void unregister(String id) {
         activeConnections.remove(id);

examples/tcp-proxy/src/main/java/one/microproject/tcp/server/impl/TcpMain.java

@@ -18,17 +18,19 @@ public class TcpMain implements Runnable, AutoCloseable {
     private final ExecutorService processors;
     private final String targetHost;
     private final Integer targetPort;
+    private final Integer maxConnections;
 
     private boolean active;
 
     public TcpMain(ConnectionRegistry connectionRegistry, ServerSocket serverSocket,
-                   ExecutorService processors, String targetHost, Integer targetPort) {
+                   ExecutorService processors, String targetHost, Integer targetPort, Integer maxConnections) {
         this.connectionRegistry = connectionRegistry;
         this.processors = processors;
         this.serverSocket = serverSocket;
         this.targetHost = targetHost;
         this.targetPort = targetPort;
         this.active = true;
+        this.maxConnections = maxConnections;
     }
 
     @Override
@@ -37,6 +39,12 @@ public void run() {
             while (active) {
                 LOG.info("Waiting for incoming TCP connections ...");
                 Socket clientSocket = serverSocket.accept();
+                LOG.info("TCP connection accepted !");
+                if (connectionRegistry.getActiveConnections() >= maxConnections) {
+                    LOG.info("Max connections {} per server exceeded, closing connection {}:{} !", maxConnections, clientSocket.getRemoteSocketAddress(), clientSocket.getPort());
+                    clientSocket.close();
+                    continue;
+                }
                 String id = UUID.randomUUID().toString();
                 LOG.info("Connection id={} from {}:{} to {}:{} in progress ...", id, clientSocket.getRemoteSocketAddress(), clientSocket.getPort(), targetHost, targetPort);
                 try (Socket socket = new Socket(targetHost, targetPort)) {
@@ -50,8 +58,13 @@ public void run() {
                 }
             }
         } catch (IOException e) {
-            LOG.info("TcpMain IOException");
+            LOG.error("TcpMain IOException: ", e);
             this.active = false;
+            try {
+                close();
+            } catch (Exception ex) {
+                LOG.error("TcpMain Exception: ", e);
+            }
         }
     }
 
@@ -60,6 +73,7 @@ public void close() throws Exception {
         LOG.info("Closing TCP Server ...");
         this.active = false;
         this.serverSocket.close();
+        this.processors.shutdown();
     }
 
 }

examples/tcp-proxy/tcp-proxy-config.json

@@ -6,7 +6,8 @@
       "serverHost": "0.0.0.0",
       "serverPort": 4567,
       "targetHost": "192.168.44.101",
-      "targetPort": 22
+      "targetPort": 22,
+      "maxConnections": 2
     }
   ]
 }