Initial data commit

Task/Chat-server/Java/chat-server.java

@@ -0,0 +1,152 @@
+import java.io.*;
+import java.net.*;
+import java.util.*;
+
+public class ChatServer implements Runnable
+{
+  private int port = 0;
+  private List<Client> clients = new ArrayList<Client>();
+
+  public ChatServer(int port)
+  {  this.port = port;  }
+
+  public void run()
+  {
+    try
+    {
+      ServerSocket ss = new ServerSocket(port);
+      while (true)
+      {
+        Socket s = ss.accept();
+        new Thread(new Client(s)).start();
+      }
+    }
+    catch (Exception e)
+    {  e.printStackTrace();  }
+  }
+
+  private synchronized boolean registerClient(Client client)
+  {
+    for (Client otherClient : clients)
+      if (otherClient.clientName.equalsIgnoreCase(client.clientName))
+        return false;
+    clients.add(client);
+    return true;
+  }
+
+  private void deregisterClient(Client client)
+  {
+    boolean wasRegistered = false;
+    synchronized (this)
+    {  wasRegistered = clients.remove(client);  }
+    if (wasRegistered)
+      broadcast(client, "--- " + client.clientName + " left ---");
+  }
+
+  private synchronized String getOnlineListCSV()
+  {
+    StringBuilder sb = new StringBuilder();
+    sb.append(clients.size()).append(" user(s) online: ");
+    for (int i = 0; i < clients.size(); i++)
+      sb.append((i > 0) ? ", " : "").append(clients.get(i).clientName);
+    return sb.toString();
+  }
+
+  private void broadcast(Client fromClient, String msg)
+  {
+    // Copy client list (don't want to hold lock while doing IO)
+    List<Client> clients = null;
+    synchronized (this)
+    {  clients = new ArrayList<Client>(this.clients);  }
+    for (Client client : clients)
+    {
+      if (client.equals(fromClient))
+        continue;
+      try
+      {  client.write(msg + "\r\n");  }
+      catch (Exception e)
+      {  }
+    }
+  }
+
+  public class Client implements Runnable
+  {
+    private Socket socket = null;
+    private Writer output = null;
+    private String clientName = null;
+
+    public Client(Socket socket)
+    {
+      this.socket = socket;
+    }
+
+    public void run()
+    {
+      try
+      {
+        socket.setSendBufferSize(16384);
+        socket.setTcpNoDelay(true);
+        BufferedReader input = new BufferedReader(new InputStreamReader(socket.getInputStream()));
+        output = new OutputStreamWriter(socket.getOutputStream());
+        write("Please enter your name: ");
+        String line = null;
+        while ((line = input.readLine()) != null)
+        {
+          if (clientName == null)
+          {
+            line = line.trim();
+            if (line.isEmpty())
+            {
+              write("A name is required. Please enter your name: ");
+              continue;
+            }
+            clientName = line;
+            if (!registerClient(this))
+            {
+              clientName = null;
+              write("Name already registered. Please enter your name: ");
+              continue;
+            }
+            write(getOnlineListCSV() + "\r\n");
+            broadcast(this, "+++ " + clientName + " arrived +++");
+            continue;
+          }
+          if (line.equalsIgnoreCase("/quit"))
+            return;
+          broadcast(this, clientName + "> " + line);
+        }
+      }
+      catch (Exception e)
+      {  }
+      finally
+      {
+        deregisterClient(this);
+        output = null;
+        try
+        {  socket.close();  }
+        catch (Exception e)
+        {  }
+        socket = null;
+      }
+    }
+
+    public void write(String msg) throws IOException
+    {
+      output.write(msg);
+      output.flush();
+    }
+
+    public boolean equals(Client client)
+    {
+      return (client != null) && (client instanceof Client) && (clientName != null) && (client.clientName != null) && clientName.equals(client.clientName);
+    }
+  }
+
+  public static void main(String[] args)
+  {
+    int port = 4004;
+    if (args.length > 0)
+      port = Integer.parseInt(args[0]);
+    new ChatServer(port).run();
+  }
+}