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Signaling Quickstart

Updated

Rapidly develop your first Signaling app.

Use Signaling SDK to add low-latency, high-concurrency signaling and synchronization capabilities to your app.

Signaling also helps you enhance the user experience in Video Calling, Voice Calling, Interactive Live Streaming, and Broadcast Streaming applications.

This page shows you how to use the Signaling SDK to rapidly build a simple application that sends and receives messages. It shows you how to integrate the Signaling SDK in your project and implement pub/sub messaging through Message channels. To get started with stream channels, follow this guide to create a basic Signaling app and then refer to the Stream channels guide.

Understand the tech

To use Signaling features in your app, you initialize a Signaling client instance and add event listeners. To connect to Signaling, you login using an authentication token. To send a message to a message channel, you publish the message. Signaling creates a channel when a user subscribes to it. To receive messages other users publish to a channel, your app listens for events.

To create a pub/sub session for Signaling, implement the following steps in your app:

Prerequisites

To implement the code presented on this page you need to have:

  • A device running Linux Ubuntu 14.04 or above; 18.04+ is recommended.
  • At least 2 GB of memory.
  • cmake 3.6.0 or above.
  • Ensure that a firewall is not blocking your network communication.

Signaling 2.x is an enhanced version compared to 1.x with a wide range of new features. It follows a new pricing structure. See Pricing for details.

Project setup

Create a project

Create the following folder structure for your project:

RTMProject/
├── include/
└── lib/

Integrate the SDK

To integrate the Linux C++ Signaling SDK into your project:

  1. Download the latest version of the SDK and unzip it.

    To integrate Signaling SDK 2.2.1 or later, and Video SDK 4.3.0 or later in the same project, refer to handle integration issues.

  2. Copy the files in the SDK package to the project folder as follows:

    • Copy the /rtm/sdk/libagora_rtm_sdk.so file to the project's lib folder.
    • Copy all *.h files in /rtm/sdk/high_level_api/include to the project's include folder.

  3. To use CMake to compile the project, create the following files in the RTMProject folder:

    • CMakeLists.txt

      # CMakeLists.txt
cmake_minimum_required (VERSION 2.8)
project(RTMProject)
set(TARGET_NAME RTMQuickStart)
set(SOURCES RTMQuickStart.cpp)
set(HEADERS)
set(TARGET_BUILD_TYPE "Debug")
set(CMAKE_CXX_FLAGS "-fPIC -O2 -g -std=c++11 -msse2")
include_directories(${CMAKE_SOURCE_DIR}/include)
link_directories(${CMAKE_SOURCE_DIR}/lib)
add_executable(${TARGET_NAME} ${SOURCES} ${HEADERS})
target_link_libraries(${TARGET_NAME} agora_rtm_sdk pthread)

    • clean_build.sh

      # clean_build.sh
rm -fr build
mkdir -p build
cd build
cmake ..
make
cd ..

Implement Signaling

A complete code sample that implements the basic features of Signaling is presented here for your reference. To use the sample code, create a new file named RTMQuickStart.cpp in the RTMProject folder and add the following code:

Complete sample code for Signaling

#include <iostream>
#include <memory>
#include <string>
#include <exception>
//#include <unistd.h>

#include "IAgoraRtmClient.h"

// Pass in your App ID and token
const std::string APP_ID = "<Your App ID>";
const std::string TOKEN = "<Your token>";

// Terminal color codes for UBUNTU/LINUX
#define RESET   "\\033\[0m"
#define BLACK   "\\033\[30m"      /* Black */
#define RED     "\\033\[31m"      /* Red */
#define GREEN   "\\033\[32m"      /* Green */
#define YELLOW  "\\033\[33m"      /* Yellow */
#define BLUE    "\\033\[34m"      /* Blue */
#define MAGENTA "\\033\[35m"      /* Magenta */
#define CYAN    "\\033\[36m"      /* Cyan */
#define WHITE   "\\033\[37m"      /* White */
#define BOLDBLACK   "\\033\[1m\\033\[30m"      /* Bold Black */
#define BOLDRED     "\\033\[1m\\033\[31m"      /* Bold Red */
#define BOLDGREEN   "\\033\[1m\\033\[32m"      /* Bold Green */
#define BOLDYELLOW  "\\033\[1m\\033\[33m"      /* Bold Yellow */
#define BOLDBLUE    "\\033\[1m\\033\[34m"      /* Bold Blue */
#define BOLDMAGENTA "\\033\[1m\\033\[35m"      /* Bold Magenta */
#define BOLDCYAN    "\\033\[1m\\033\[36m"      /* Bold Cyan */
#define BOLDWHITE   "\\033\[1m\\033\[37m"      /* Bold White */

using namespace agora::rtm;

class RtmEventHandler : public IRtmEventHandler {
public:
  // Add the event listener
  void onLoginResult(const uint64_t requestId, RTM_ERROR_CODE errorCode) override {
    cbPrint("onLoginResult, request id: %lld, errorCode: %d", requestId, errorCode);
  }

  void onLogoutResult(const uint64_t requestId, RTM_ERROR_CODE errorCode) {
    cbPrint("onLogoutResult, request id: %lld, errorCode: %d", requestId, errorCode);
  }

  void onConnectionStateChanged(const char *channelName, RTM_CONNECTION_STATE state, RTM_CONNECTION_CHANGE_REASON reason) override {
    cbPrint("onConnectionStateChanged, channelName: %s, state: %d, reason: %d", channelName, state, reason);
  }

  void onLinkStateEvent(const LinkStateEvent& event) override {
    cbPrint("onLinkStateEvent, state: %d -> %d, operation: %d, reason: %s", event.previousState, event.currentState, event.operation, event.reason);
  }

  void onPublishResult(const uint64_t requestId, RTM_ERROR_CODE errorCode) override {
    cbPrint("onPublishResult request id: %lld result: %d", requestId, errorCode);
  }

  void onMessageEvent(const MessageEvent &event) override {
    cbPrint("receive message from: %s, message: %s", event.publisher, event.message);
  }

  void onSubscribeResult(const uint64_t requestId, const char *channelName, RTM_ERROR_CODE errorCode) override {
    cbPrint("onSubscribeResult: channel:%s, request id: %lld result: %d", channelName, requestId, errorCode);
  }

  void onUnsubscribeResult(const uint64_t requestId, const char *channelName, RTM_ERROR_CODE errorCode) override {
    cbPrint("onUnsubscribeResult: channel:%s, request id: %lld result: %d", channelName, requestId, errorCode);
  }

private:
  void cbPrint(const char* fmt, ...) {
    printf("\\x1b[32m<< RTM async callback: ");
    va_list args;
    va_start(args, fmt);
    vprintf(fmt, args);
    va_end(args);
    printf(" >>\\x1b[0m\\n");
  }
};

class RtmDemo {
public:
  RtmDemo()
    : eventHandler_(new RtmEventHandler()),
      rtmClient_(nullptr) { Init(); }

  void Init() {
    std::cout << YELLOW << "Please enter userID (literal \\"null\\" or starting"
    << "with space is not allowed, no more than 64 characters!):" << std::endl;

    std::string userID;
    std::getline(std::cin, userID);

    RtmConfig config;
    config.appId = APP_ID.c_str();
    config.userId = userID.c_str();
    config.eventHandler = eventHandler_.get();
    // Create an IRtmClient instance
    int errorCode = 0;
    rtmClient_ = createAgoraRtmClient(config, errorCode);
    if (!rtmClient_ || errorCode != 0) {
      std::cout << RED <<"error creating rtm service!" << std::endl;
      exit(0);
    }
  }

  void start() {
    // Log in the RTM server
    uint64_t requestId = 0;
    rtmClient_->login(TOKEN.c_str(), requestId);

    // Sample codes for the user interface
    mainMeun();

    std::cout << YELLOW << "quit ? yes/no" << std::endl;
    std::string input;
    std::getline(std::cin, input);
    if (input.compare("yes") == 0) {
      exit(0);
    }
  }

  // Log out from the RTM server
  void logout() {
    uint64_t requestId = 0;
    rtmClient_->logout(requestId);
  }

  // Subscribe to a channel
  void subscribeChannel(const std::string& channelName) {
    uint64_t requestId = 0;
    rtmClient_->subscribe(channelName.c_str(), SubscribeOptions(), requestId);
  }

  // Unsubscribe from a channel
  void unsubscribeChannel(const std::string& channelName) {
    uint64_t requestId = 0;
    rtmClient_->unsubscribe(channelName.c_str(), requestId);
  }

  // Publish a message
  void publishMessage(const std::string& channelName, const std::string& message) {
    PublishOptions options;
    options.messageType = RTM_MESSAGE_TYPE_STRING;
    uint64_t requestId;
    rtmClient_->publish(channelName.c_str(), message.c_str(), message.size(), options, requestId);
  }

  // Sample codes for the user interface
  void mainMeun() {
    bool quit  = false;
    while (!quit) {
      std::cout << WHITE
                << "1: subscribe channel\\n"
                << "2: unsubscribe channel\\n"
                << "3: publish message\\n"
                << "4: logout" << std::endl;
      std::cout << YELLOW <<"please input your choice: " << std::endl;
      std::string input;
      std::getline(std::cin, input);
      int32_t choice = 0;
      try {
        choice = std::stoi(input);
      } catch(...) {
        std::cout <<RED << "invalid input" << std::endl;
        continue;
      }

      switch (choice)
      {
        case 1: {
          std::cout << YELLOW << "please input channel name:" << std::endl;
          std::string channelName;
          std::getline(std::cin, channelName);
          subscribeChannel(channelName);
          std::this_thread::sleep_for(std::chrono::seconds(1));
          break;
        }
        case 2: {
          std::cout << YELLOW << "please input channel name:" << std::endl;
          std::string channelName;
          std::getline(std::cin, channelName);
          unsubscribeChannel(channelName);
          std::this_thread::sleep_for(std::chrono::seconds(1));
          break;
        }
        case 3: {
          std::cout << YELLOW << "please input channel name:" << std::endl;
          std::string channelName;
          std::getline(std::cin, channelName);
          groupChat(channelName);
          break;
        }
        case 4: {
          logout();
          return;
        }
        default: {
          std::cout <<RED << "invalid input" << std::endl;
          break;
        }
      }
    }
  }

  void groupChat(const std::string& channelName) {
    std::string message;
    while (true) {
      std::cout << YELLOW << "please input message "
                << "or input \\"quit\\" to leave group chat"
                << std::endl;
      std::getline(std::cin, message);
      if (message.compare("quit") == 0) {
        return;
      } else {
        publishMessage(channelName, message);
        std::this_thread::sleep_for(std::chrono::seconds(1));
      }
    }
  }

private:
  std::unique_ptr<IRtmEventHandler> eventHandler_;
  IRtmClient* rtmClient_;
};

int main(int argc, const char * argv[]) {
  RtmClient messaging;
  messaging.login();
  return 0;
}

Follow the implementation steps to understand the core API calls in the sample code or use the snippets in your own code.

Include the header file

To use Signaling APIs in your project, include the IAgoraRtmClient header file:

#include "IAgoraRtmClient.h"

Initialize the Signaling engine

Before calling any other Signaling SDK API, initialize an IRtmClient object instance.

std::string userID;
std::getline(std::cin, userID);

RtmConfig config;
config.appId = APP_ID.c_str();
config.userId = userID.c_str();
config.eventHandler = eventHandler_.get();

// Create an IRtmClient instance
int errorCode = 0;
rtmClient_ = createAgoraRtmClient(config, errorCode);
if (!rtmClient_ || errorCode != 0) {
  std::cout << RED <<"error creating rtm service!" << std::endl;
  exit(0);
}

Add an event listener

The event listener enables you to implement the processing logic in response to Signaling events. Use the following code to handle event notifications or display received messages:

void onLoginResult(const uint64_t requestId, RTM_ERROR_CODE errorCode) override {
  cbPrint("onLoginResult, request id: %lld, errorCode: %d", requestId, errorCode);
}

void onLogoutResult(const uint64_t requestId, RTM_ERROR_CODE errorCode) {
  cbPrint("onLogoutResult, request id: %lld, errorCode: %d", requestId, errorCode);
}

void onConnectionStateChanged(const char *channelName, RTM_CONNECTION_STATE state, RTM_CONNECTION_CHANGE_REASON reason) override {
  cbPrint("onConnectionStateChanged, channelName: %s, state: %d, reason: %d", channelName, state, reason);
}

void onLinkStateEvent(const LinkStateEvent& event) override {
  cbPrint("onLinkStateEvent, state: %d -> %d, operation: %d, reason: %s", event.previousState, event.currentState, event.operation, event.reason);
}

void onPublishResult(const uint64_t requestId, RTM_ERROR_CODE errorCode) override {
  cbPrint("onPublishResult request id: %lld result: %d", requestId, errorCode);
}

void onMessageEvent(const MessageEvent &event) override {
  cbPrint("receive message from: %s, message: %s", event.publisher, event.message);
}

void onSubscribeResult(const uint64_t requestId, const char *channelName, RTM_ERROR_CODE errorCode) override {
  cbPrint("onSubscribeResult: channel:%s, request id: %lld result: %d", channelName, requestId, errorCode);
}

void onUnsubscribeResult(const uint64_t requestId, const char *channelName, RTM_ERROR_CODE errorCode) override {
  cbPrint("onUnsubscribeResult: channel:%s, request id: %lld result: %d", channelName, requestId, errorCode);
}

Log in to Signaling

To connect to Signaling and access Signaling network resources, such as sending messages, and subscribing to channels, call login.

During a login operation, the client attempts to establish a connection with Signaling. Once the connection is established, the client transmits heartbeat information to the Signaling server at fixed intervals to keep the client active until the client actively logs out or is disconnected. The connection is interrupted when timeout occurs. During this period, users may freely access the Signaling network resources subject to their own permissions and usage restrictions.

// Log in to Signaling
uint64_t requestId = 0;
rtmClient_->login(TOKEN.c_str(), requestId);

After you call this method, the SDK triggers the onLoginResult callback and returns the API call result.

Use the login return value, or listen to the onConnectionStateChanged event notification to confirm that login is successful or obtain the error code and cause of login failure. When performing a login operation, the client's network connection state is RTM_CONNECTION_STATE_CONNECTING. After a successful login, the state is updated to RTM_CONNECTION_STATE_CONNECTED.

Best practice

To continuously monitor the network connection state of the client, best practice is to continue to listen for onConnectionStateChanged event notifications throughout the life cycle of the application. For further details, see Event listeners.

After a user successfully logs into Signaling, the application's PCU increases, which affects your billing data.

Send a message

To distribute a message to all subscribers of a message channel, call publish. The following code sends a string type message.

// Publish a message to the channel
void publishMessage(const std::string& channelName, const std::string& message) {
  PublishOptions options;
  options.messageType = RTM_MESSAGE_TYPE_STRING;
  uint64_t requestId;
  rtmClient_->publish(channelName.c_str(), message.c_str(), message.size(), options, requestId);
}

Before calling publish to send a message, serialize the message payload as a string.

Subscribe and unsubscribe

To receive messages sent to a channel, call subscribe to subscribe to channel messages:

// Subscribe to a channel
void subscribeChannel(const std::string& channelName) {
  uint64_t requestId = 0;
  rtmClient_->subscribe(channelName.c_str(), SubscribeOptions(), requestId);
}

When you no longer need to receive messages from a channel, call unsubscribe to unsubscribe from the channel:

// Unsubscribe from a channel
void unsubscribeChannel(const std::string& channelName) {
  uint64_t requestId = 0;
  rtmClient_->unsubscribe(channelName.c_str(), requestId);
}

For more information about sending and receiving messages see Message channels and Stream channels.

Log out of Signaling

When a user no longer needs to use Signaling, call logout. Logging out means closing the connection between the client and Signaling. The user is automatically logged out or unsubscribed from all message and stream channels. Other users in the channel receive an onPresenceEvent notification of the user leaving the channel.

// Log out of Signaling
void logout() {
  uint64_t requestId = 0;
  rtmClient_->logout(requestId);
}

// Clean up
rtmClient_->release();

Test Signaling

Take the following steps to test the sample code:

  1. Use the Token Builder to generate a Signaling token:

    1. Select Signaling from the Agora products dropdown.
    2. Fill in your app ID and app certificate from Agora Console. Leave the remaining fields blank.
    3. Click Generate Token.

  2. In your code, replace <Your App ID> with your app ID from Agora Console and <Your token> with the generated token. Save the project. Make sure Signaling is activated for your project in Agora Console.

  3. In the terminal, run the following command to compile the project:

    sh +x clean_build.sh

  4. Use the following commands to navigate to the build folder and run the app:

    cd build
./RTMQuickStart

    You see menu options to subscribe, unsubscribe, publish, and logout.

  5. Follow the prompts to subscribe to a channel.

  6. Run another instance of the app using a different user ID. Follow the prompts to publish a message to the same channel that you subscribed to from the other instance.

  7. You see the message displayed in the instance that you used to subscribe to the channel.

    Congratulations! You have successfully integrated Signaling into your project.

Reference

This section contains content that completes the information on this page, or points you to documentation that explains other aspects to this product.

Token authentication

In this guide you retrieve a temporary token from a Token Builder. To understand how to create an authentication server for development purposes, see Secure authentication with tokens.

Sample project

Agora provides an open source sample project on GitHub for your reference. Download it or view the source code for a more detailed example.

API reference

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