Add a tcp chat server implementation example

examples/tcp-chat-server/.gitignore

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+# Ballerina generates this directory during the compilation of a package.
+# It contains compiler-generated artifacts and the final executable if this is an application package.
+target/
+
+# Ballerina maintains the compiler-generated source code here.
+# Remove this if you want to commit generated sources.
+generated/
+
+# Contains configuration values used during development time.
+# See https://ballerina.io/learn/provide-values-to-configurable-variables/ for more details.
+Config.toml

examples/tcp-chat-server/Ballerina.toml

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+[build-options]
+observabilityIncluded = true

examples/tcp-chat-server/Dependencies.toml

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+# AUTO-GENERATED FILE. DO NOT MODIFY.
+
+# This file is auto-generated by Ballerina for managing dependency versions.
+# It should not be modified by hand.
+
+[ballerina]
+dependencies-toml-version = "2"
+distribution-version = "2201.10.3"
+
+[[package]]
+org = "ballerina"
+name = "crypto"
+version = "2.7.2"
+dependencies = [
+	{org = "ballerina", name = "jballerina.java"},
+	{org = "ballerina", name = "time"}
+]
+
+[[package]]
+org = "ballerina"
+name = "io"
+version = "1.6.3"
+dependencies = [
+	{org = "ballerina", name = "jballerina.java"},
+	{org = "ballerina", name = "lang.value"}
+]
+modules = [
+	{org = "ballerina", packageName = "io", moduleName = "io"}
+]
+
+[[package]]
+org = "ballerina"
+name = "jballerina.java"
+version = "0.0.0"
+
+[[package]]
+org = "ballerina"
+name = "lang.regexp"
+version = "0.0.0"
+dependencies = [
+	{org = "ballerina", name = "jballerina.java"}
+]
+
+[[package]]
+org = "ballerina"
+name = "lang.string"
+version = "0.0.0"
+dependencies = [
+	{org = "ballerina", name = "jballerina.java"},
+	{org = "ballerina", name = "lang.regexp"}
+]
+modules = [
+	{org = "ballerina", packageName = "lang.string", moduleName = "lang.string"}
+]
+
+[[package]]
+org = "ballerina"
+name = "lang.value"
+version = "0.0.0"
+dependencies = [
+	{org = "ballerina", name = "jballerina.java"}
+]
+
+[[package]]
+org = "ballerina"
+name = "observe"
+version = "1.3.0"
+dependencies = [
+	{org = "ballerina", name = "jballerina.java"}
+]
+
+[[package]]
+org = "ballerina"
+name = "tcp"
+version = "1.11.2"
+dependencies = [
+	{org = "ballerina", name = "crypto"},
+	{org = "ballerina", name = "jballerina.java"}
+]
+modules = [
+	{org = "ballerina", packageName = "tcp", moduleName = "tcp"}
+]
+
+[[package]]
+org = "ballerina"
+name = "time"
+version = "2.5.0"
+dependencies = [
+	{org = "ballerina", name = "jballerina.java"}
+]
+
+[[package]]
+org = "ballerinai"
+name = "observe"
+version = "0.0.0"
+dependencies = [
+	{org = "ballerina", name = "jballerina.java"},
+	{org = "ballerina", name = "observe"}
+]
+modules = [
+	{org = "ballerinai", packageName = "observe", moduleName = "observe"}
+]
+
+[[package]]
+org = "user"
+name = "tcp_chat_server"
+version = "0.1.0"
+dependencies = [
+	{org = "ballerina", name = "io"},
+	{org = "ballerina", name = "lang.string"},
+	{org = "ballerina", name = "tcp"},
+	{org = "ballerinai", name = "observe"}
+]
+modules = [
+	{org = "user", packageName = "tcp_chat_server", moduleName = "tcp_chat_server"}
+]
+

examples/tcp-chat-server/README.md

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+# TCP Chat Server
+
+[![Star on Github](https://img.shields.io/badge/-Star%20on%20Github-blue?style=social&logo=github)](https://github.com/ballerina-platform/module-ballerina-tcp)
+
+## Overview
+
+A simple TCP chat server implementation in Ballerina that allows multiple clients to connect and exchange messages. Each message is broadcast to all connected clients with a sequential message number.
+
+## Features
+
+- Supports multiple concurrent client connections
+- Broadcasts messages to all connected clients
+- Sequential message numbering
+- Handles client disconnections gracefully
+- Welcome message for new clients
+
+## Run the Server
+
+```sh
+# Start the server
+$ bal run
+```
+
+## Connect as Client
+
+You can connect using either telnet or netcat:
+
+```sh
+# Using telnet
+$ telnet localhost 3000
+
+# Using netcat
+$ nc localhost 3000
+```
+
+## Testing
+
+1. Open multiple terminal windows
+2. Start the server in one terminal
+3. Connect multiple clients using telnet/netcat in other terminals
+4. Type messages in any client terminal and press Enter
+5. Observe the broadcast messages in all client terminals
+
+Each message will be prefixed with a sequential number and broadcast to all connected clients.
+
+## Implementation Details
+
+The server uses Ballerina's TCP module to:
+
+- Listen for incoming connections on port 3000
+- Maintain a map of connected clients
+- Buffer incoming messages until newline
+- Broadcast messages to all connected clients
+- Handle client disconnections

examples/tcp-chat-server/main.bal

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+import ballerina/io;
+import ballerina/tcp;
+import ballerina/lang.'string;
+
+type ChatServer service object {
+    map<tcp:Caller> clients;
+    public int messageCount;
+    remote function onConnect(tcp:Caller caller) returns tcp:ConnectionService|tcp:Error;
+};
+
+service class ChatServerImpl {
+    *ChatServer;
+    map<tcp:Caller> clients = {};
+    public int messageCount = 0;
+
+    remote function onConnect(tcp:Caller caller) returns tcp:ConnectionService|tcp:Error {
+        self.clients[caller.id] = caller;
+        io:println("New client connected");
+        string welcomeMsg = "Welcome!,\r\nSend your first message: \r\n";
+        check caller->writeBytes(welcomeMsg.toBytes());
+        return new ChatConnectionService(caller.id, self.clients, self);
+    }
+}
+
+service on new tcp:Listener(3000) {
+    private final ChatServerImpl chatServer = new;
+
+    remote function onConnect(tcp:Caller caller) returns tcp:ConnectionService|tcp:Error {
+        return self.chatServer->onConnect(caller);
+    }
+}
+
+service class ChatConnectionService {
+    *tcp:ConnectionService;
+    private final string callerId;
+    private final map<tcp:Caller> clients;
+    private final ChatServerImpl parent;
+    private string messageBuffer = "";
+
+    public function init(string callerId, map<tcp:Caller> clients, ChatServerImpl parent) {
+        self.callerId = callerId;
+        self.clients = clients;
+        self.parent = parent;
+    }
+
+    remote function onBytes(readonly & byte[] data) returns tcp:Error? {
+        string|error message = 'string:fromBytes(data);
+        if message is error {
+            return;
+        }
+
+        self.messageBuffer += message;
+        if self.messageBuffer.includes("\n") {
+            string[] messages = re`\r?\n`.split(self.messageBuffer);
+            self.messageBuffer = messages[messages.length() - 1];
+
+            foreach string msg in messages.slice(0, messages.length() - 1) {
+                if msg.trim() != "" {
+                    self.parent.messageCount += 1;
+                    string broadcastMsg = string `Message #${self.parent.messageCount}: ${msg}` + "\r\nNew message:\r\n";
+                    foreach tcp:Caller caller in self.clients {
+                        check caller->writeBytes(broadcastMsg.toBytes());
+                    }
+                }
+            }
+        }
+    }
+
+    remote function onError(tcp:Error err) {
+        io:println("Error occurred: ", err.message());
+    }
+
+    remote function onClose() {
+        _ = self.clients.remove(self.callerId);
+        io:println("Client disconnected");
+    }
+}