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Commit de7eb223 authored by Terry D. Norbraten's avatar Terry D. Norbraten
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use try w/ resources

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examples/src/TcpExamples/TcpExample2ConnectionCounting.java
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...@@ -33,7 +33,7 @@ public class TcpExample2ConnectionCounting ...@@ -33,7 +33,7 @@ public class TcpExample2ConnectionCounting
// ServerSocket waits for a connection from a client. // ServerSocket waits for a connection from a client.
// Notice that it is outside the loop; ServerSocket needs to be made only once. // Notice that it is outside the loop; ServerSocket needs to be made only once.
int connectionCount = 0; // state variable int connectionCount = 0; // state variable
ServerSocket serverSocket = new ServerSocket(2317); // server decides here what port to listen on. ServerSocket serverSocket = new ServerSocket(2317); // server decides here what port to listen on.
// of interest: often client doesn't care what port it uses locally when connecting to that server port. // of interest: often client doesn't care what port it uses locally when connecting to that server port.
...@@ -42,53 +42,53 @@ public class TcpExample2ConnectionCounting ...@@ -42,53 +42,53 @@ public class TcpExample2ConnectionCounting
// Stop the program somewhere else. // Stop the program somewhere else.
while(true) while(true)
{ {
Socket clientConnection = serverSocket.accept(); // blocks! then proceeds once a connection is "accept"ed // blocks! then proceeds once a connection is "accept"ed
try (Socket clientConnection = serverSocket.accept()) {
connectionCount++; // got another one! connectionCount++; // got another one!
OutputStream os = clientConnection.getOutputStream(); OutputStream os = clientConnection.getOutputStream();
PrintStream ps = new PrintStream(os); PrintStream ps = new PrintStream(os);
ps.println("This client response was written by server TcpExample2ConnectionCounting"); // to remote client ps.println("This client response was written by server TcpExample2ConnectionCounting"); // to remote client
System.out.println("This server response was written by server TcpExample2ConnectionCounting"); // to server console System.out.println("This server response was written by server TcpExample2ConnectionCounting"); // to server console
ps.println("You were connection #" + connectionCount + ", by my count"); ps.println("You were connection #" + connectionCount + ", by my count");
// Print some information locally about the Socket connection. // Print some information locally about the Socket connection.
// This includes the port and IP numbers on both sides (the socket pair.) // This includes the port and IP numbers on both sides (the socket pair.)
InetAddress localAddress = clientConnection.getLocalAddress(); InetAddress localAddress = clientConnection.getLocalAddress();
InetAddress remoteAddress = clientConnection.getInetAddress(); InetAddress remoteAddress = clientConnection.getInetAddress();
int localPort = clientConnection.getLocalPort(); int localPort = clientConnection.getLocalPort();
int remotePort = clientConnection.getPort(); // remember the prior question, why are 2 ports different? int remotePort = clientConnection.getPort(); // remember the prior question, why are 2 ports different?
// My socket pair connection looks like this, to localhost: // My socket pair connection looks like this, to localhost:
// Socket pair: (( /0:0:0:0:0:0:0:1, 2317 ), ( /0:0:0:0:0:0:0:1, 54876 )) note IPv6 // Socket pair: (( /0:0:0:0:0:0:0:1, 2317 ), ( /0:0:0:0:0:0:0:1, 54876 )) note IPv6
// Socket pair: (( /0:0:0:0:0:0:0:1, 2317 ), ( /0:0:0:0:0:0:0:1, 54881 )) // Socket pair: (( /0:0:0:0:0:0:0:1, 2317 ), ( /0:0:0:0:0:0:0:1, 54881 ))
// //
// Why is first IP/port the same, while the second set has different ports? // Why is first IP/port the same, while the second set has different ports?
System.out.println("Socket pair: (( " + localAddress.toString() + ", " + localPort + " ), ( " + System.out.println("Socket pair: (( " + localAddress.toString() + ", " + localPort + " ), ( " +
remoteAddress.toString() + ", " + remotePort + " ))"); remoteAddress.toString() + ", " + remotePort + " ))");
System.out.println("got another connection, #" + connectionCount); // report progress System.out.println("got another connection, #" + connectionCount); // report progress
// Notice the use of flush() and close(). Without // Notice the use of flush() and close(). Without
// the close() to Socket object may stay open for // the close() to Socket object may stay open for
// a while after the client has stopped needing this // a while after the client has stopped needing this
// connection. Close() explicitly ends the connection. // connection. Close() explicitly ends the connection.
ps.flush(); ps.flush();
clientConnection.close(); } // got another one!
} }
} }
catch(IOException e) catch(IOException e)
{ {
System.out.println("Problem with TcpExample2ConnectionCounting networking:"); // describe what is happening System.err.println("Problem with TcpExample2ConnectionCounting networking:"); // describe what is happening
System.out.println("Error: " + e); System.err.println("Error: " + e);
// Provide more helpful information to user if exception occurs due to running twice at one time // Provide more helpful information to user if exception occurs due to running twice at one time
if (e instanceof java.net.BindException) if (e instanceof java.net.BindException)
System.out.println("*** Be sure to stop any other running instances of programs using this port!"); System.err.println("*** Be sure to stop any other running instances of programs using this port!");
} }
} }
} }
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