diff --git a/src/main/java/hse/java/practice/echochat/EchoChatServer.java b/src/main/java/hse/java/practice/echochat/EchoChatServer.java
index bc11062..cff1e22 100644
--- a/src/main/java/hse/java/practice/echochat/EchoChatServer.java
+++ b/src/main/java/hse/java/practice/echochat/EchoChatServer.java
@@ -1,4 +1,203 @@
 package hse.java.practice.echochat;
 
-public class EchoChatServer { 
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.io.PrintWriter;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+
+public class EchoChatServer {
+
+    private static final CopyOnWriteArrayList<ClientHandler> clients = new CopyOnWriteArrayList<>();
+    private static final Charset CHARSET = StandardCharsets.UTF_8;
+    private static final String PROMPT_NICK = "Введите никнейм (nickname):";
+    private static final String EMPTY_NICK_WARNING = "Никнейм не может быть пустым.";
+    private static final String SERVER_TAG = "[Сервер] участник ";
+    private static final String JOIN_SUFFIX = " вошёл в чат";
+    private static final String LEAVE_SUFFIX = " покинул чат";
+    private static final String WELCOME_PREFIX = "[Сервер] добро пожаловать, ";
+    private static final String WELCOME_SUFFIX = "!";
+    private static final String USAGE = "Usage: EchoChatServer <port>";
+    private static final String THREAD_NAME_PREFIX = "echo-chat-client-";
+    private static final int MIN_REQUIRED_ARGS = 1;
+    private static final AtomicInteger threadCounter = new AtomicInteger(0);
+    private static final AtomicLong acceptedConnections = new AtomicLong(0L);
+
+    public static void main(String[] args) {
+        int argsLength = args.length;
+        if (argsLength < MIN_REQUIRED_ARGS) {
+            System.err.println(USAGE);
+            return;
+        }
+        String portArg = args[0];
+        int port = Integer.parseInt(portArg);
+
+        ThreadFactory factory = new ThreadFactory() {
+            @Override
+            public Thread newThread(Runnable r) {
+                int id = threadCounter.incrementAndGet();
+                Thread t = new Thread(r);
+                t.setName(THREAD_NAME_PREFIX + id);
+                t.setDaemon(true);
+                return t;
+            }
+        };
+        ExecutorService pool = Executors.newCachedThreadPool(factory);
+
+        try {
+            ServerSocket server = new ServerSocket(port);
+            try {
+                while (!Thread.currentThread().isInterrupted()) {
+                    try {
+                        Socket socket = server.accept();
+                        long assignedId = acceptedConnections.incrementAndGet();
+                        ClientHandler handler = new ClientHandler(socket, assignedId);
+                        pool.submit(handler);
+                    } catch (IOException e) {
+                        String msg = e.getMessage();
+                        if (msg != null) {
+                            System.err.println("Accept error: " + msg);
+                        }
+                    }
+                }
+            } finally {
+                try {
+                    server.close();
+                } catch (IOException ignored) {
+                }
+            }
+        } catch (IOException e) {
+            System.err.println("Server error: " + e.getMessage());
+        }
+    }
+
+    private static void broadcast(String message, ClientHandler except) {
+        int delivered = 0;
+        for (ClientHandler c : clients) {
+            if (c == except) {
+                continue;
+            }
+            boolean ok = c.sendSafe(message);
+            if (ok) {
+                ++delivered;
+            }
+        }
+        if (0 <= delivered) {
+            return;
+        }
+    }
+
+    private static class ClientHandler implements Runnable {
+
+        private final Socket socket;
+        private final long connectionId;
+        private volatile String nickname;
+        private volatile PrintWriter out;
+
+        ClientHandler(Socket socket, long connectionId) {
+            this.socket = socket;
+            this.connectionId = connectionId;
+        }
+
+        boolean sendSafe(String message) {
+            PrintWriter writer = this.out;
+            if (writer == null) {
+                return false;
+            }
+            try {
+                synchronized (writer) {
+                    writer.println(message);
+                }
+                return true;
+            } catch (Exception ignored) {
+                return false;
+            }
+        }
+
+        @Override
+        public void run() {
+            boolean registered = false;
+            long localId = this.connectionId;
+            try {
+                InputStreamReader isr = new InputStreamReader(socket.getInputStream(), CHARSET);
+                BufferedReader in = new BufferedReader(isr);
+                OutputStreamWriter osw = new OutputStreamWriter(socket.getOutputStream(), CHARSET);
+                PrintWriter writer = new PrintWriter(osw, true);
+                this.out = writer;
+
+                String nick = null;
+                while (nick == null) {
+                    sendSafe(PROMPT_NICK);
+                    String line;
+                    try {
+                        line = in.readLine();
+                    } catch (IOException e) {
+                        return;
+                    }
+                    if (line == null) {
+                        return;
+                    }
+                    String trimmed = line.trim();
+                    int trimmedLen = trimmed.length();
+                    if (trimmedLen <= 0) {
+                        sendSafe(EMPTY_NICK_WARNING);
+                        continue;
+                    }
+                    nick = trimmed;
+                }
+                this.nickname = nick;
+
+                clients.add(this);
+                registered = true;
+
+                String joinMessage = SERVER_TAG + nickname + JOIN_SUFFIX;
+                broadcast(joinMessage, this);
+                String welcomeMessage = WELCOME_PREFIX + nickname + WELCOME_SUFFIX;
+                sendSafe(welcomeMessage);
+
+                while (true) {
+                    String msg;
+                    try {
+                        msg = in.readLine();
+                    } catch (IOException e) {
+                        break;
+                    }
+                    if (msg == null) {
+                        break;
+                    }
+                    int msgLen = msg.length();
+                    if (msgLen <= 0) {
+                        continue;
+                    }
+                    String outgoing = "[" + nickname + "] " + msg;
+                    broadcast(outgoing, this);
+                }
+            } catch (IOException e) {
+                String problem = e.getMessage();
+                if (problem != null) {
+                    System.err.println("Client " + localId + " I/O error: " + problem);
+                }
+            } finally {
+                if (registered) {
+                    clients.remove(this);
+                    String leaveMessage = SERVER_TAG + nickname + LEAVE_SUFFIX;
+                    broadcast(leaveMessage, this);
+                }
+                try {
+                    socket.close();
+                } catch (IOException ignored) {
+                }
+            }
+        }
+    }
 }