Java tutorial
//The 3 classes are a a tcp client, tcp server, and a Serializable payload object which is sent from the server to the client.
//The 3 classes are meant to work together.
//--George
//TcpClient.java -------------------------------------------------------------------------------------------------------------------------
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.net.Socket;
import java.net.UnknownHostException;
/**
* TcpClient.java
*
* This class works in conjunction with TcpServer.java and TcpPayload.java
*
* This client test class connects to server class TcpServer, and in response,
* it receives a serialized an instance of TcpPayload.
*/
public class TcpClient
{
public final static String SERVER_HOSTNAME = "gsoler.arc.nasa.gov";
public final static int COMM_PORT = 5050; // socket port for client comms
private Socket socket;
private TcpPayload payload;
/** Default constructor. */
public TcpClient()
{
try
{
this.socket = new Socket(SERVER_HOSTNAME, COMM_PORT);
InputStream iStream = this.socket.getInputStream();
ObjectInputStream oiStream = new ObjectInputStream(iStream);
this.payload = (TcpPayload) oiStream.readObject();
}
catch (UnknownHostException uhe)
{
System.out.println("Don't know about host: " + SERVER_HOSTNAME);
System.exit(1);
}
catch (IOException ioe)
{
System.out.println("Couldn't get I/O for the connection to: " +
SERVER_HOSTNAME + ":" + COMM_PORT);
System.exit(1);
}
catch(ClassNotFoundException cne)
{
System.out.println("Wanted class TcpPayload, but got class " + cne);
}
System.out.println("Received payload:");
System.out.println(this.payload.toString());
}
/**
* Run this class as an application.
*/
public static void main(String[] args)
{
TcpClient tcpclient = new TcpClient();
}
}
TcpServer.java-------------------------------------------------------------------------------------------------------------------------
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
/**
* This class works in conjunction with TcpClient.java and TcpPayload.java
*
* This server test class opens a socket on localhost and waits for a client
* to connect. When a client connects, this server serializes an instance of
* TcpPayload and sends it to the client.
*/
public class TcpServer
{
public final static int COMM_PORT = 5050; // socket port for client comms
private ServerSocket serverSocket;
private InetSocketAddress inboundAddr;
private TcpPayload payload;
/** Default constructor. */
public TcpServer()
{
this.payload = new TcpPayload();
initServerSocket();
try
{
while (true)
{
// listen for and accept a client connection to serverSocket
Socket sock = this.serverSocket.accept();
OutputStream oStream = sock.getOutputStream();
ObjectOutputStream ooStream = new ObjectOutputStream(oStream);
ooStream.writeObject(this.payload); // send serilized payload
ooStream.close();
Thread.sleep(1000);
}
}
catch (SecurityException se)
{
System.err.println("Unable to get host address due to security.");
System.err.println(se.toString());
System.exit(1);
}
catch (IOException ioe)
{
System.err.println("Unable to read data from an open socket.");
System.err.println(ioe.toString());
System.exit(1);
}
catch (InterruptedException ie) { } // Thread sleep interrupted
finally
{
try
{
this.serverSocket.close();
}
catch (IOException ioe)
{
System.err.println("Unable to close an open socket.");
System.err.println(ioe.toString());
System.exit(1);
}
}
}
/** Initialize a server socket for communicating with the client. */
private void initServerSocket()
{
this.inboundAddr = new InetSocketAddress(COMM_PORT);
try
{
this.serverSocket = new java.net.ServerSocket(COMM_PORT);
assert this.serverSocket.isBound();
if (this.serverSocket.isBound())
{
System.out.println("SERVER inbound data port " +
this.serverSocket.getLocalPort() +
" is ready and waiting for client to connect...");
}
}
catch (SocketException se)
{
System.err.println("Unable to create socket.");
System.err.println(se.toString());
System.exit(1);
}
catch (IOException ioe)
{
System.err.println("Unable to read data from an open socket.");
System.err.println(ioe.toString());
System.exit(1);
}
}
/**
* Run this class as an application.
*/
public static void main(String[] args)
{
TcpServer tcpServer = new TcpServer();
}
}
TcpPayload.java-------------------------------------------------------------------------------------------------------------------------
import java.io.Serializable;
/**
* This class works in conjunction with TcpClient.java and TcpServer.java
*
* This class contains test data representing a 'payload' that is sent from
* TcpServer to TcpClient. An object of this class is meant to be serialized by
* the server before being sent to the client. An object of this class is meant
* to be deserialized by the client after being received.
*/
public class TcpPayload implements Serializable
{
// serial version UID was generated with serialver command
static final long serialVersionUID = -50077493051991107L;
private int int1;
private transient int int2; // transient members are not serialized
private float float1;
private double double1;
private short short1;
private String str1;
private long long1;
private char char1;
/** Default constructor. */
public TcpPayload()
{
this.int1 = 123;
this.int2 = 456;
this.float1 = -90.05f;
this.double1 = 55.055;
this.short1 = 59;
this.str1 = "I am a String payload.";
this.long1 = -23895901L;
this.char1 = 'x';
}
/** Get a String representation of this class. */
public String toString()
{
StringBuilder strB = new StringBuilder();
strB.append("int1=" + this.int1);
strB.append(" int2=" + this.int2);
strB.append(" float1=" + this.float1);
strB.append(" double1=" + this.double1);
strB.append(" short1=" + this.short1);
strB.append(" str1=" + this.str1);
strB.append(" long1=" + this.long1);
strB.append(" char1=" + this.char1);
return strB.toString();
}
}