Initial commit

.gitignore

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+out/

chat-server.iml

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+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="library" name="KotlinJavaRuntime" level="project" />
+    <orderEntry type="library" name="org.java-websocket:Java-WebSocket:1.4.0" level="project" />
+  </component>
+</module>

src/Main.kt

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+import org.java_websocket.WebSocket
+import org.java_websocket.handshake.ClientHandshake
+import org.java_websocket.server.WebSocketServer
+import java.net.InetSocketAddress
+
+class ChatServer(port: Int) : WebSocketServer(InetSocketAddress(port)) {
+
+    private var nextId = 0
+
+    override fun onOpen(connection: WebSocket, handshake: ClientHandshake?) {
+        val id = ++nextId
+
+        println("#$id connected")
+        connection.setAttachment(id)
+    }
+
+    override fun onClose(connection: WebSocket, code: Int, reason: String?, remote: Boolean) {
+        println("#${connection.getAttachment<Int>()} disconnected")
+    }
+
+    override fun onMessage(connection: WebSocket, message: String) {
+        val toClientMessage = "${connection.getAttachment<Int>()}: $message"
+
+        connections.filter(WebSocket::isOpen).forEach { openedConnection ->
+            try {
+                openedConnection.send(toClientMessage)
+            } catch (t: Throwable) {
+            }
+        }
+    }
+
+    override fun onStart() {
+        println("server starts on port $port")
+    }
+
+    override fun onError(connection: WebSocket, e: Exception?) {
+        println("error: $e")
+    }
+}
+
+object Main {
+
+    @JvmStatic
+    fun main(vararg args: String) {
+        val server = ChatServer(DEFAULT_PORT).apply {
+            start()
+        }
+
+        Runtime.getRuntime().addShutdownHook(object : Thread() {
+
+            override fun run() {
+                server.stop()
+            }
+        })
+    }
+
+    private const val DEFAULT_PORT = 8885
+}