Socket Communication Question

Question

Hi, I am new to using sockets and somewhat new to Java in general.
How does one go about setting up a client/server system so that:
- The server will wait for connections
- After it accepts the connection, will read the first request sent
- After interpreting this request, I'd like to send a reponse BACK to the client
- After receiving this response, the client will UPLOAD a file over the socket
I've got a https server a client running, but it is more of a single response per request kind of setup. Sorry if this seems like a silly question, I am somewhat new.
Chuck Reed

Answer 1

* PingServer.java
* Created on December 1, 2001, 1:47 PM
package com.sas.planetation.servers.ping;
import com.sas.util.socket.*;
import com.sas.planetation.data.*;
import com.sas.planetation.exceptions.*;
import com.sas.planetation.servers.*;
import java.io.*;
import java.util.*;
import java.net.*;
* @author  Scott Shaver
* @version
public class PingServer implements ClientConnectionHandler, CommandInputListener{
    public static final String CONFIG_FILE_NAME = "pingserver.cfg";
    public static final String PROP_LISTEN_PORT = "pingserver.listeningport";
    public static final String PROP_ADMIN_PORT = "pingserver.adminport";
    public static final String PROP_BYTE_COUNT = "pingserver.sendbytecount";
    private Properties properties = null;
    private MultiSocketServer pingSocket = null;
    private MultiSocketServer adminSocket = null;
    private int pingPort = 0;
    private int adminPort = 0;
    private int pingByteCount = 0;
    private CommandInput cmdInput = null;
    private String configDirectory = null;
    /** Creates new PingServer */
    public PingServer(String configDir) {
        super();
        configDirectory = configDir;
    public void setPingSocket(MultiSocketServer server) {
        pingSocket = server;
    public void setAdminSocket(MultiSocketServer server) {
        adminSocket = server;
    public MultiSocketServer getPingSocket() {
        return pingSocket;
    public MultiSocketServer getAdminSocket() {
        return adminSocket;
    public void setPingByteCount(int count) {
        pingByteCount = count;
    public void setPingPort(int port) {
        pingPort = port;
    public void setAdminPort(int port) {
        adminPort = port;
    public int getPingPort() {
        return pingPort;
    public int getAdminPort() {
        return adminPort;
    public Properties getProperties() {
        return properties;
    public void startUp() {
        try
            postMessage("-------------------------------------");
            postMessage("Planetation Ping Server");
            postMessage("-------------------------------------");
            postMessage("Loading configuration.");
            properties = loadConfiguration();
            String data = getProperties().getProperty(PROP_BYTE_COUNT);
            int bc = Integer.parseInt(data.trim());
            if(bc<0 || bc>127)
                bc=1;
            postMessage("Setting ping byte count to "+bc+".");
            if(data!=null)
                setPingByteCount(bc);
            data = getProperties().getProperty(PROP_LISTEN_PORT);
            if(data!=null)
                setPingPort(Integer.parseInt(data.trim()));
            postMessage("Setting client listening port to "+getPingPort()+".");
            setPingSocket(new MultiSocketServer(this,getPingPort()));
            postMessage("Starting client listening thread.");
            getPingSocket().start();
            data = getProperties().getProperty(PROP_ADMIN_PORT);
            if(data!=null)
                setAdminPort(Integer.parseInt(data.trim()));
            postMessage("Setting admin listening port to "+getAdminPort()+".");
            setAdminSocket(new MultiSocketServer(this,getAdminPort()));
            postMessage("Starting admin listening thread.");
            getAdminSocket().start();
            postMessage("Server is started and ready.");
            postMessage("-------------------------------------");
            cmdInput = new CommandInput(this);
            cmdInput.startUp();
        catch(Exception x)
            postMessage("Error during server boot.\n"+x);
            System.exit(0);
    * @param args the command line arguments
    public static void main (String args[]) {
        if(args.length!=1)
            System.out.println("Error: Directory location of the config file must be provided.");
            return;
        PingServer ps = new PingServer(args[0]);
        ps.startUp();
    public void postMessage(String msg) {
        System.out.println(msg);
    public Properties loadConfiguration() throws ConfigNotFoundException {
        Properties properties = new Properties();
        File cf = new File(configDirectory,CONFIG_FILE_NAME);
        if(!cf.canRead())
            throw new ConfigNotFoundException("Read permissions not set for "+cf.toString()+".");
        try
            FileInputStream fis = new FileInputStream(cf);
            BufferedInputStream bis = new BufferedInputStream(fis);
            properties.load(bis);
            bis.close();
        catch(Exception x)
            throw new ConfigNotFoundException("Error reading "+cf.toString()+".\n"+x);
        return properties;
     * Called when a client connection is accepted in the run method.
     * Sub-classes of this class should define this method to handle
     * the client requests. Note that while this method is being executed
     * no more client connections will be accepted so this method must
     * complete quickly.
    public void handleClientConnection(SocketServer server, Socket s) {
        if(server.getPort()==getPingPort())
            postMessage("Received client connection.");
            PingServerClientThread ct = new PingServerClientThread(s,pingByteCount);
        else if(server.getPort()==getAdminPort())
            postMessage("Received admin connection.");
            try
                DataInputStream is = new DataInputStream(s.getInputStream());
                int type = is.readInt();
                switch(type)
                    case CommunicationDataTypes.SERVER_STOP:
                        ServerStop ss = new ServerStop();
                        ss.readData(is);
                        shutDownServer();
                        break;
            catch(IOException x)
                postMessage("Error reading admin connection data.\n"+x);
            catch(InvalidFileFormatException iffx)
                postMessage("Error reading admin connection data. InvalidFileFormatException\n"+iffx);
    public void shutDownServer() {
        postMessage("Stopping server.");
        pingSocket.stop();
        adminSocket.stop();
        cmdInput.stop();
        System.exit(0);
    public void handleCommandInput(String cmd) {
        postMessage("Processing Command: "+cmd);
        if(cmd.equals("stop"))
            shutDownServer();
        else if(cmd.equals("?") || cmd.equals("help"))
            postMessage("stop - shutdown the server");
            postMessage("? or help - show the command help");
        else
            postMessage("Command is not recognized. Type help or ? for command list.");
}