diff --git a/assignments/src/MV3500Cohort2020JulySeptember/homework2/White/WhiteClient.java b/assignments/src/MV3500Cohort2020JulySeptember/homework2/White/WhiteClient.java new file mode 100644 index 0000000000000000000000000000000000000000..9589ac93f3886d65ab11752b9b1543dc9df1c103 --- /dev/null +++ b/assignments/src/MV3500Cohort2020JulySeptember/homework2/White/WhiteClient.java @@ -0,0 +1,83 @@ +package MV3500Cohort2020JulySeptember.homework2.White; + +import java.io.*; +import java.net.*; + +/** + * Before, we always used telnet (netcat) to connect to the server. Here we are + * now writing our own program to do the connection. + * + * As you will see, when we run this after we start the server we will see the + * same string telnet printed, sent by the server. The output at the server will + * show different socket pairs for each time the loop iterates. + * + * @author mcgredo + * @author brutzman + */ +public class WhiteClient { + + // IPv6 String constant for localhost address, similarly IPv4 127.0.0.1 + public final static String LOCALHOST = "0:0:0:0:0:0:0:1"; + + public static void main(String[] args) { + + // Local variables/fields + Socket socket; + InputStream is; + InputStreamReader isr; + BufferedReader br; + OutputStream os; + PrintStream ps; + String serverMessage; + int clientLoopCount = 0; + + try { + while (true) + { + + System.out.println("White Client creating socket..."); + + // We request an IP to connect to ("localhost") and + // port number at that IP (2317). This establishes + // a connection to that IP in the form of a Socket + // object; the server uses a ServerSocket to wait for + // connections. + socket = new Socket(LOCALHOST, 2317); // locohost? + + os = socket.getOutputStream(); + ps = new PrintStream(os); + ps.println("I AM A CLIENT!"); // this gets sent back to client! + // Now hook everything up (i.e. set up the streams), Java style: + is = socket.getInputStream(); + isr = new InputStreamReader(is); + br = new BufferedReader(isr); + + // Read a single line written by the server. We'd + // do things a bit differently if there were many lines to be read + // from the server instead of one only. + serverMessage = br.readLine(); + System.out.println("=================================================="); + + System.out.println("The message the server sent was: '" + serverMessage + "'"); + // socket gets closed, either automatically/silently by this code (or possibly by the server) + + } // end while(true) + } + catch (IOException e) + { + System.err.println("Problem with White Server networking:"); // describe what is happening + System.err.println("Error: " + e); + + // Provide more helpful information to user if exception occurs due to running twice at one time + if (e instanceof java.net.BindException) { + System.err.println("*** Be sure to stop any other running instances of programs using this port!"); + } + } + finally // occurs after any other activity when shutting down + { + // program exit: tell somebody about that happening. Likely cause: server drops connection. + System.out.println(); + System.out.println("White Client exit"); + } + } +} diff --git a/assignments/src/MV3500Cohort2020JulySeptember/homework2/White/WhiteServer.java b/assignments/src/MV3500Cohort2020JulySeptember/homework2/White/WhiteServer.java new file mode 100644 index 0000000000000000000000000000000000000000..2ad0350ffd9334db551662f799233206cd7fbba1 --- /dev/null +++ b/assignments/src/MV3500Cohort2020JulySeptember/homework2/White/WhiteServer.java @@ -0,0 +1,112 @@ +package MV3500Cohort2020JulySeptember.homework2.White; + +import java.io.*; +import java.net.*; + +/** + * Very slightly more complex than example1, further modifying example2. The + * only thing this does differently is introduce a loop into the response, so + * you don't have to restart the program after one response. Also, it prints out + * the socket pair the server sees. Run the program via telnet several times and + * compare the socket pairs. + * + * telnet (nc) localhost 2317 + * + * If you're sophisticated you can contact the instructor's computer while + * running this program. + * + * telnet (nc) [ipNumberOfServerLaptop] 2317 + * + * and have the instructor display the socket pairs received. + * + * @author mcgredo + * @author brutzman + */ +public class WhiteServer { + + public static void main(String[] args) { + try { + + // ServerSocket waits for a connection from a client. + // Notice that it is outside the loop; ServerSocket + // needs to be made only once. + System.out.println("White Server has started..."); // it helps debugging to put this on console first + + ServerSocket serverSocket = new ServerSocket(2317); + OutputStream os; + PrintStream ps; + InputStream is; + InputStreamReader isr; + BufferedReader br; + String clientMessage; + InetAddress localAddress, remoteAddress; + int localPort, remotePort; + int serverLoopCount = 0; + + // Server is up and waiting (i.e. "blocked" or paused) + // Loop, infinitely, waiting for client connections. + // Stop the program somewhere else. + while (true) { + + // block until connected to a client + try (Socket clientConnectionSocket = serverSocket.accept()) + { + + // Now hook everything up (i.e. set up the streams), Java style: + os = clientConnectionSocket.getOutputStream(); + ps = new PrintStream(os); + ps.println("I AM A SERVER!"); // this gets sent back to client! + + // Print some information locally about the Socket connection. + // This includes the port and IP numbers on both sides (the socket pair). + localAddress = clientConnectionSocket.getLocalAddress(); + remoteAddress = clientConnectionSocket.getInetAddress(); + localPort = clientConnectionSocket.getLocalPort(); + remotePort = clientConnectionSocket.getPort(); + + + // 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 )) + // Socket pair: (( /0:0:0:0:0:0:0:1, 2317 ), ( /0:0:0:0:0:0:0:1, 54881 )) + + // Why is the first IP/port the same, while the second set has different ports? + System.out.println("White Server socket pair showing host name, address, port:"); + System.out.println(" (( " + + localAddress.getHostName() + "=" + localAddress.getHostAddress() + ", " + localPort + " ), ( " + + remoteAddress.getHostName() + "=" + remoteAddress.getHostAddress() + ", " + remotePort + " ))"); + + + is = clientConnectionSocket.getInputStream(); + isr = new InputStreamReader(is); + br = new BufferedReader(isr); + + // Read a single line written by the server. We'd + // do things a bit differently if there were many lines to be read + // from the server instead of one only. + clientMessage = br.readLine(); + System.out.println("=================================================="); + + System.out.println("The message the client sent was: '" + clientMessage + "'"); + + if ( localAddress.getHostName().equals( localAddress.getHostAddress()) || + remoteAddress.getHostName().equals(remoteAddress.getHostAddress())) + System.out.println(" note HostName matches address if host has no DNS name"); + + // Notice the use of flush() and try w/ resources. Without + // the try w/ resources the Socket object may stay open for + // a while after the client has stopped needing this + // connection. try w/ resources explicitly ends the connection. + ps.flush(); + // like it or not, you're outta here! + } + } + } catch (IOException e) { + System.err.println("Problem with White Server networking: " + e); + + // Provide more helpful information to user if exception occurs due to running twice at one time + if (e instanceof java.net.BindException) { + System.err.println("*** Be sure to stop any other running instances of programs using this port!"); + } + } + } +}