Added Null check to Close Methods, Added Proxy config for TCP Sender & enable SSL hostname verification

src/main/java/com/cloudbees/syslog/sender/TcpSyslogMessageSender.java

@@ -19,11 +19,14 @@
 import com.cloudbees.syslog.util.CachingReference;
 import com.cloudbees.syslog.util.IoUtils;
 
+import com.cloudbees.syslog.sender.proxy.ProxyConfig;
+
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
 import javax.net.SocketFactory;
 import javax.net.ssl.SSLContext;
+import javax.net.ssl.SSLParameters;
 import javax.net.ssl.SSLSession;
 import javax.net.ssl.SSLSocket;
 import javax.net.ssl.SSLSocketFactory;
@@ -70,6 +73,13 @@ public class TcpSyslogMessageSender extends AbstractSyslogMessageSender implemen
     private int socketConnectTimeoutInMillis = SETTING_SOCKET_CONNECT_TIMEOUT_IN_MILLIS_DEFAULT_VALUE;
     private boolean ssl;
     private SSLContext sslContext;
+    private ProxyConfig proxyConfig;
+    /**
+     * If the last connection was via a proxy server this will contain the 
+     * InetAddress of the syslog server that was connected to via the proxy.
+     */
+    private InetAddress proxyConnectedSyslogServer;
+
     /**
      * Number of retries to send a message before throwing an exception.
      */
@@ -122,9 +132,36 @@ public synchronized void sendMessage(@Nonnull SyslogMessage message) throws IOEx
         }
     }
 
+    /**
+     * @return true if not proxy connected and the socket is connected to current configured syslog 
+     */
+    private boolean notProxyConnectedAddressChange(final InetAddress inetAddress) {
+    	return proxyConnectedSyslogServer == null && !Objects.equals(socket.getInetAddress(), inetAddress);
+    }
+
+    /**
+     * @return true if currentProxyConfig status does not match proxyConnectedSyslogServer
+     */
+    private boolean proxyUseHasChanged(final ProxyConfig currentProxyConfig) {
+    	return (currentProxyConfig != null && proxyConnectedSyslogServer == null)
+		|| (currentProxyConfig == null && proxyConnectedSyslogServer != null);
+    }
+
+    /**
+     * @return true if proxy connected and either proxy connection or syslog server connection have changed
+     */
+    private boolean proxyConnectedAddressChange(final InetAddress syslogServer, final ProxyConfig currentProxyConfig) {
+    	return proxyConnectedSyslogServer != null && (!Objects.equals(syslogServer, proxyConnectedSyslogServer) 
+    			|| !Objects.equals(socket.getInetAddress(), currentProxyConfig.getHostnameReference().get()));
+    }
+
     private synchronized void ensureSyslogServerConnection() throws IOException {
         InetAddress inetAddress = syslogServerHostnameReference.get();
-        if (socket != null && !Objects.equals(socket.getInetAddress(), inetAddress)) {
+        final ProxyConfig currentProxyConfig = this.proxyConfig;
+        if (socket != null && (
+        		notProxyConnectedAddressChange(inetAddress)
+        		|| proxyUseHasChanged(currentProxyConfig)
+        		|| proxyConnectedAddressChange(inetAddress, currentProxyConfig))) {
             logger.info("InetAddress of the Syslog Server have changed, create a new connection. " +
                     "Before=" + socket.getInetAddress() + ", new=" + inetAddress);
             IoUtils.closeQuietly(socket, writer);
@@ -145,19 +182,44 @@ private synchronized void ensureSyslogServerConnection() throws IOException {
         if (!socketIsValid) {
             writer = null;
             try {
-                if (ssl) {
+            	final SocketFactory socketFactory;
+            	if (ssl) {
                     if (sslContext == null) {
-                        socket = SSLSocketFactory.getDefault().createSocket();
+                    	socketFactory = SSLSocketFactory.getDefault();
                     } else {
-                        socket = sslContext.getSocketFactory().createSocket();
+                    	socketFactory = sslContext.getSocketFactory();
                     }
                 } else {
-                    socket = SocketFactory.getDefault().createSocket();
+                	socketFactory = SocketFactory.getDefault();
                 }
-                socket.setKeepAlive(true);
-                socket.connect(
-                        new InetSocketAddress(inetAddress, syslogServerPort),
-                        socketConnectTimeoutInMillis);
+
+            	final InetSocketAddress syslogServer = new InetSocketAddress(inetAddress, syslogServerPort);
+
+            	if(currentProxyConfig == null) {
+            		socket = socketFactory.createSocket();
+            		socket.setKeepAlive(true);
+            		socket.connect(
+                    		syslogServer,
+                            socketConnectTimeoutInMillis);
+            		proxyConnectedSyslogServer = null;
+            	}else {
+            		final InetSocketAddress proxyAddr = new InetSocketAddress(currentProxyConfig.getHostnameReference().get(), currentProxyConfig.getPort());
+            		final Socket underlying = new Socket(new Proxy(Proxy.Type.HTTP, proxyAddr));
+            		underlying.setKeepAlive(true);
+            		underlying.connect(syslogServer);
+                    socket = ((SSLSocketFactory)socketFactory).createSocket(
+                          underlying,
+                          syslogServer.getHostName(),
+                          syslogServer.getPort(),
+                          true);
+                    socket.setKeepAlive(true);
+                    final SSLSocket sslSocket = (SSLSocket) socket;
+                    final SSLParameters sslParams = new SSLParameters();
+                    sslParams.setEndpointIdentificationAlgorithm("HTTPS");
+                    sslSocket.setSSLParameters(sslParams);
+                    proxyConnectedSyslogServer = inetAddress;
+            	}
+
 
                 if (socket instanceof SSLSocket && logger.isLoggable(Level.FINER)) {
                     try {
@@ -241,7 +303,15 @@ public synchronized SSLContext getSSLContext() {
         return this.sslContext; 
     }
 
-    public int getSocketConnectTimeoutInMillis() {
+    public ProxyConfig getProxyConfig() {
+		return proxyConfig;
+	}
+
+	public void setProxyConfig(ProxyConfig proxyConfig) {
+		this.proxyConfig = proxyConfig;
+	}
+
+	public int getSocketConnectTimeoutInMillis() {
         return socketConnectTimeoutInMillis;
     }
 
@@ -287,6 +357,7 @@ public String toString() {
 
     @Override
     public void close() throws IOException {
-        this.socket.close();
+        if(this.socket != null)
+        	this.socket.close();
     }
 }

src/main/java/com/cloudbees/syslog/sender/UdpSyslogMessageSender.java

@@ -151,6 +151,7 @@ public String toString() {
 
     @Override
     public void close() throws IOException {
-        this.datagramSocket.close();
+    	if(this.datagramSocket != null)
+    		this.datagramSocket.close();
     }
 }

src/main/java/com/cloudbees/syslog/sender/proxy/ProxyConfig.java

@@ -0,0 +1,46 @@
+package com.cloudbees.syslog.sender.proxy;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+import javax.annotation.Nullable;
+
+import com.cloudbees.syslog.sender.SyslogMessageSender;
+import com.cloudbees.syslog.util.CachingReference;
+
+public class ProxyConfig {
+
+	private final int port;
+	private final String hostname;
+	private final CachingReference<InetAddress> hostnameReference;
+
+	public ProxyConfig (final int port, final String hostname) {
+		this.port = port;
+		this.hostname = hostname;
+        this.hostnameReference = new CachingReference<InetAddress>(SyslogMessageSender.DEFAULT_INET_ADDRESS_TTL_IN_NANOS) {
+            @Nullable
+            @Override
+            protected InetAddress newObject() {
+                try {
+                    return InetAddress.getByName(hostname);
+                } catch (UnknownHostException e) {
+                    throw new IllegalStateException(e);
+                }
+            }
+        };
+	}
+
+	public int getPort() {
+		return port;
+	}
+
+	public String getHostname() {
+		return hostname;
+	}
+
+	public CachingReference<InetAddress> getHostnameReference() {
+		return hostnameReference;
+	}
+
+
+}