diff --git a/assignments/src/MV3500Cohort2021JulySeptember/homework1/SchlesselTcpExample1Telnet.java b/assignments/src/MV3500Cohort2021JulySeptember/homework1/SchlesselTcpExample1Telnet.java new file mode 100644 index 0000000000000000000000000000000000000000..fa2565785de76a5753d4368ab87c75adce506373 --- /dev/null +++ b/assignments/src/MV3500Cohort2021JulySeptember/homework1/SchlesselTcpExample1Telnet.java @@ -0,0 +1,65 @@ +package TcpExamples; + +import java.io.*; +import java.net.*; + +/** + * Homework 1 + * + * @author max schlessel + */ +public class SchlesselTcpExample1Telnet +{ + /** + * Program invocation, execution starts here + * @param args command-line arguments + */ + public static void main(String[] args) + { + try + { + System.out.println(SchlesselTcpExample1Telnet.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(" enter (telnet localhost 2317) or (nc localhost 2317)..." ); + + // The ServerSocket waits for a connection from a client. + // It returns a Socket object when the connection occurs. + ServerSocket serverSocket = new ServerSocket(2317); + + // Use Java io classes to write text (as opposed to + // unknown bytes of some sort) to the client + + // The Socket object represents the connection between + // the server and client, including a full duplex connection + try (Socket clientConnection = serverSocket.accept()) // wait here for a client to connect + { + // OK we got something, time to respond! + // Use Java io classes to write text (as opposed to + // unknown bytes of some sort) to the client + OutputStream os = clientConnection.getOutputStream(); + PrintStream ps = new PrintStream(os); + + ps.println("This client response was written by Max's client " + SchlesselTcpExample1Telnet.class.getName()); // to remote client + ps.println("aka the shot heard round the world"); + System.out.println("This server response was written by Max's server " + SchlesselTcpExample1Telnet.class.getName()); // to server console + System.out.println("boom"); + + // "flush()" in important in that it forces a write + // across what is in fact a slow connection + ps.flush(); + } + System.out.println(SchlesselTcpExample1Telnet.class.getName() + " completed successfully."); + } + catch(IOException e) + { + System.err.println("Exception with " + SchlesselTcpExample1Telnet.class.getName() + " networking:"); // describe what is happening + System.err.println(e); + // Provide more helpful information to user if exception occurs due to running twice at one time + + // brute force exception checking, can be brittle if exception message changes + // if (e.getMessage().equals("Address already in use: NET_Bind")) + if (e instanceof java.net.BindException) + System.err.println("*** Be sure to stop any other running instances of programs using this port!"); + } + } +}