From bfa6e988d3ea277dc2a5289ae968fa3b1613063b Mon Sep 17 00:00:00 2001
From: brutzman <brutzman@nps.edu>
Date: Tue, 23 Jul 2024 10:42:53 -0700
Subject: [PATCH] improved comments and variable naming
---
.../TcpExample2ConnectionCounting.java | 59 +++++++++++--------
1 file changed, 36 insertions(+), 23 deletions(-)
diff --git a/examples/src/TcpExamples/TcpExample2ConnectionCounting.java b/examples/src/TcpExamples/TcpExample2ConnectionCounting.java
index de9a434599..03bb12bddf 100644
--- a/examples/src/TcpExamples/TcpExample2ConnectionCounting.java
+++ b/examples/src/TcpExamples/TcpExample2ConnectionCounting.java
@@ -63,7 +63,7 @@ public class TcpExample2ConnectionCounting
try
{
// welcome aboard messages
- System.out.println("TcpExample2ConnectionCounting has started and is waiting for a connection.");
+ System.out.println(TcpExample2ConnectionCounting.class.getName() + " has started and is waiting for a connection.");
System.out.println(" help: https://savage.nps.edu/Savage/developers.html#telnet");
System.out.println(" Windows ipconfig (or Mac ifconfig) indicates current IPv4_Address (for example local wireless IP address)");
System.out.println(" Windows enter (telnet localhost 2317) or Mac enter (nc localhost 2317) for loopback operation, or" );
@@ -76,18 +76,22 @@ public class TcpExample2ConnectionCounting
int connectionCount = 0; // state variable
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.
+
+ OutputStream outputStream; // can declare these early, but...
+ PrintStream printStream; // note initial values are null, they still need to be intialized
// Loop, infinitely, waiting for client connections.
- // Stop the program somewhere else.
+ // If you want to stop or pause the program, go somewhere else.
while(true)
{
- // serverSocket.accept() blocks! then proceeds once a connection is "accept"ed
- try (Socket clientConnection = serverSocket.accept()) { // the accept() method blocks here until a client connects
+ // note that serverSocket.accept() first blocks! then after waiting, execution proceeds once a connection is "accept"ed
+ // you can check this behavior by using NetBeans Debugger
+ try (Socket clientConnectionSocket = serverSocket.accept()) { // the accept() method blocks here until a client connects
connectionCount++; // got another one! a client has connected
- OutputStream os = clientConnection.getOutputStream();
- PrintStream ps = new PrintStream(os);
+ outputStream = clientConnectionSocket.getOutputStream(); // clientConnectionSocket is new, every time through, so reset the streams
+ printStream = new PrintStream(outputStream);
// if (connectionCount == 1) // first time through, report connection
// {
@@ -104,19 +108,19 @@ public class TcpExample2ConnectionCounting
// "(telnet " + localHostAddress + " 2317)..." );
// }
- ps.println("This client response was written by server " + TcpExample2ConnectionCounting.class.getName()); // to remote client
- System.out.println("This server response was written by server " + TcpExample2ConnectionCounting.class.getName()); // to server console
+ printStream.println("This client response was written by server " + TcpExample2ConnectionCounting.class.getName()); // to remote client
+ System.out.println("This server response was written by server " + TcpExample2ConnectionCounting.class.getName()); // to server console
- ps.println("You were connection #" + connectionCount + ", by my count");
+ printStream.println("You were connection #" + connectionCount + ", by my count");
// Print some information locally about the Socket connection.
// This includes the port and IP numbers on both sides (the socket pair.)
- InetAddress localAddress = clientConnection.getLocalAddress();
- InetAddress remoteAddress = clientConnection.getInetAddress();
+ InetAddress localAddress = clientConnectionSocket.getLocalAddress();
+ InetAddress remoteAddress = clientConnectionSocket.getInetAddress();
- int localPort = clientConnection.getLocalPort();
- int remotePort = clientConnection.getPort(); // remember the prior question, why are 2 ports different?
+ int localPort = clientConnectionSocket.getLocalPort();
+ int remotePort = clientConnectionSocket.getPort(); // remember the prior question, why are 2 ports different?
// 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
@@ -125,25 +129,34 @@ public class TcpExample2ConnectionCounting
// Why is first IP/port the same, while the second set has different ports?
System.out.println("Socket pair (server, client): (( " + localAddress.toString() + ", " + localPort + " ), ( " +
- remoteAddress.toString() + ", " + remotePort + " ))");
+ remoteAddress.toString() + ", " + remotePort + " ))");
System.out.println("got another connection, #" + connectionCount); // report progress
- // Notice the use of flush() and close(). Without
- // the close() to Socket object may stay open for
- // a while after the client has stopped needing this
- // connection. Close() explicitly ends the connection.
- ps.flush();
+ // Notice the use of flush() to ensure that messages are sent immediately,
+ // rather than possibly getting buffered for the program's self-perceived efficiency.
+ outputStream.flush();
+
+ // Notice the use of optional close() when complete. Without a close() invocation,
+ // the clientConnectionSocket object may stay open for a while after the client
+ // has stopped needing this connection. Close() explicitly ends the connection.
+ // Try hiding this and see if anything different occurs.
+ clientConnectionSocket.close();
}
}
}
- catch(IOException e)
+ catch(IOException ioe)
{
System.err.println("Problem with " + TcpExample2ConnectionCounting.class.getName() + " networking:"); // describe what is happening
- System.err.println("Error: " + e);
+ System.err.println("Error: " + ioe);
// Provide more helpful information to user if exception occurs due to running twice at one time
- if (e instanceof java.net.BindException)
+ if (ioe instanceof java.net.BindException)
System.err.println("*** Be sure to stop any other running instances of programs using this port!");
}
+ finally
+ {
+ // given the infinite-loop logic above, this step is "hard to reach" but a good practice nevertheless
+ System.out.println(TcpExample2ConnectionCounting.class.getName() + " has finished, adios!");
+ }
}
}
--
GitLab