Catch NullPointerException of Amazon AWS ELB during healthcheck

VerteilteSysteme-Examples/src/verteiltesysteme/socket/simple/TCPServer.java

@@ -1,29 +1,36 @@
-/* Angelehnt an Kurose/Ross Computernetzwerke (bis 5e Java, ab 6e Python) */
-
-package verteiltesysteme.socket.simple;
-
-import java.io.*;
-import java.net.*;
-
-class TCPServer {
-	public static void main(String argv[]) throws Exception {
-		int tcpPort = 36037;
-		String clientSentence;
-		String capitalizedSentence;
-
-		// Server-Socket erzeugen
-		@SuppressWarnings("resource")
-		ServerSocket welcomeSocket = new ServerSocket(tcpPort);
-		
-		while (true) {
-			Socket connectionSocket = welcomeSocket.accept();
-
-			BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
-			DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
-
-			clientSentence = inFromClient.readLine();
-			capitalizedSentence = clientSentence.toUpperCase() + '\n';
-			outToClient.writeBytes(capitalizedSentence);
-		}
-	}
-}
+/* Angelehnt an Kurose/Ross Computernetzwerke (bis 5e Java, ab 6e Python) */
+
+package verteiltesysteme.socket.simple;
+
+import java.io.*;
+import java.net.*;
+
+class TCPServer {
+	public static void main(String argv[]) throws Exception {
+		int tcpPort = 36037;
+		String clientSentence;
+		String capitalizedSentence;
+
+		// Server-Socket erzeugen
+		@SuppressWarnings("resource")
+		ServerSocket welcomeSocket = new ServerSocket(tcpPort);
+		
+		while (true) {
+			Socket connectionSocket = welcomeSocket.accept();
+
+			BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
+			DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
+
+			// Try/Catch hinzugefügt, nachdem bei Einsatz Amazon AWS (Healthcheck des ELB) clientSentence null war  
+			try {
+				clientSentence = inFromClient.readLine();
+				capitalizedSentence = clientSentence.toUpperCase() + '\n';
+				outToClient.writeBytes(capitalizedSentence);
+			} catch (IOException ioe) {
+				ioe.printStackTrace();
+			} catch (NullPointerException npe) {
+				npe.printStackTrace();
+			}
+		}
+	}
+}