Merge pull request #1435 from randilt/tcp-chat-server-example

Add a tcp chat server implementation example

examples/tcp-chat-server/Ballerina.toml

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+[package]
+org = "wso2"
+name = "tcp_chat_server"
+version = "0.1.0"
+distribution = "2201.10.3"
+
+[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"}
+]
+
+[[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 = "log"
+version = "2.10.0"
+dependencies = [
+	{org = "ballerina", name = "io"},
+	{org = "ballerina", name = "jballerina.java"},
+	{org = "ballerina", name = "lang.value"},
+	{org = "ballerina", name = "observe"}
+]
+modules = [
+	{org = "ballerina", packageName = "log", moduleName = "log"}
+]
+
+[[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 = "wso2"
+name = "tcp_chat_server"
+version = "0.1.0"
+dependencies = [
+	{org = "ballerina", name = "lang.string"},
+	{org = "ballerina", name = "log"},
+	{org = "ballerina", name = "tcp"},
+	{org = "ballerinai", name = "observe"}
+]
+modules = [
+	{org = "wso2", 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 broadcasted to all the connected clients with a sequential message number.
+
+## Features
+
+- Supports multiple concurrent client connections
+- Broadcasts messages to all connected clients
+- Sequential message numbering
+- Gracefully handles the client closures
+- Welcome message for new clients
+
+## Run the Server
+
+```sh
+# Start the server
+$ bal run
+```
+
+## Connect as Client
+
+You can connect using either [`telnet`](https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/telnet) or [`netcat`](https://netcat.sourceforge.net/):
+
+```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/chat_service.bal

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+// Copyright (c) 2025 WSO2 LLC. (http://www.wso2.com).
+//
+// WSO2 LLC. licenses this file to you under the Apache License,
+// Version 2.0 (the "License"); you may not use this file except
+// in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+import ballerina/lang.'string;
+import ballerina/log;
+import ballerina/tcp;
+
+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;
+        log:printInfo("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) {
+        log:printError("Error occurred", err);
+    }
+
+    remote function onClose() {
+        _ = self.clients.remove(self.callerId);
+        log:printInfo("Client disconnected");
+    }
+}