Rust API & SDK Docs 0.6.0

This guide walks you through a simple "Hello, World" application that demonstrates the core concepts of PubNub:

• Setting up a connection
• Sending messages
• Receiving messages in real-time

Overview

This guide will help you get up and running with PubNub in your Rust application. Since Rust is commonly used across different platforms, we provide two implementation paths:

• Server-side applications: For developers building backend services and applications with Rust
• Embedded systems: For developers using Rust in resource-constrained environments (embedded devices, WebAssembly)

The core PubNub concepts and API usage remain the same across both paths, but implementation details like feature selection and memory management differ. Select the appropriate tab in each section to see platform-specific guidance.

Feature selection

The Rust SDK is designed to be modular with support for different feature sets. You can enable or disable specific features based on your needs, which is especially useful for embedded systems with limited resources.

Prerequisites

Before we dive in, make sure you have:

• A basic understanding of Rust
• Rust and Cargo installed on your system
• A PubNub account (we'll help you set this up!)

Setup

Get your PubNub keys

First things first – you'll need your PubNub keys to get started. Here's how to get them:

• Sign in or create an account on the PubNub Admin Portal
• Create an app (or use an existing one)
• Find your publish and subscribe keys in the app dashboard

When you create a new app, PubNub automatically generates your first set of keys. While you can use the same keys for development and production, we recommend creating separate keysets for each environment for better security and management.

Install the SDK

SDK version

Always use the latest SDK version to have access to the newest features and avoid security vulnerabilities, bugs, and performance issues.

Server-side applications

Add pubnub to your Rust project in the Cargo.toml file:

1[dependencies]
2pubnub = "0.6.0"
3serde = "1.0"
4serde_json = "1.0"
5tokio = { version = "1", features = ["full"] }

Then in your main.rs file:

1use pubnub::dx::*;
2use pubnub::core::*;
3use serde_json::json;
4

5#[tokio::main]
6async fn main() -> Result<(), Box<dyn std::error::Error>> {
7    // Set up PubNub configuration
8    let pubnub = PubNubClientBuilder::with_reqwest_transport()
9        .with_keyset(Keyset {
10            subscribe_key: "demo",      // Replace with your subscribe key
11            publish_key: Some("demo"),  // Replace with your publish key
12            secret_key: None,
13        })
14        .with_user_id("rust-server-user")
15        .build()?;
16    
17    println!("PubNub client initialized successfully!");
18    
19    // We'll add more code here in the next steps
20    
21    Ok(())
22}

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Embedded systems

For embedded systems or WebAssembly targets, you'll want to optimize for size and disable features you don't need:

1[dependencies]
2# Disable default features and only enable what you need
3pubnub = { version = "0.6.0", default-features = false, features = ["publish"] }
4serde = { version = "1.0", default-features = false }

The pubnub crate is no_std compatible, making it suitable for embedded environments:

1[dependencies]
2# Minimal configuration for embedded systems
3pubnub = { version = "0.6.0", default-features = false, features = ["serde", "publish"] }
4serde = { version = "1.0", default-features = false }

Source code

Clone the GitHub repository:

1git clone https://github.com/pubnub/rust

Steps

Initialize PubNub

Server-side applications

In your Rust project, create a new file (e.g., main.rs) with the following content. This is the minimum configuration you need to send messages with PubNub.

Make sure to replace the placeholder keys with your publish and subscribe keys from the Admin Portal.

1use pubnub::dx::*;
2use pubnub::core::*;
3use serde_json::json;
4

5#[tokio::main]
6async fn main() -> Result<(), Box<dyn std::error::Error>> {
7    // Set up PubNub configuration
8    let pubnub = PubNubClientBuilder::with_reqwest_transport()
9        .with_keyset(Keyset {
10            subscribe_key: "demo",      // Replace with your subscribe key
11            publish_key: Some("demo"),  // Replace with your publish key
12            secret_key: None,
13        })
14        .with_user_id("rust-server-user")
15        .build()?;
16    
17    println!("PubNub client initialized successfully!");
18    
19    // We'll add more code here in the next steps
20    
21    Ok(())
22}

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Embedded systems

For embedded systems, you'll want to be more careful with memory usage. The following example shows how to structure your code, but you'll need to adapt it to your specific embedded environment:

1// Note: This is a conceptual example. 
2// You'll need to adapt this to your specific embedded target.
3

4use pubnub::dx::*;
5use pubnub::core::*;
6use pubnub::transport::*;
7

8// First, implement a transport that works with your environment
9struct MinimalTransport;
10

11impl Transport for MinimalTransport {
12    // Implement the Transport trait methods here
13    // This is a simplified example and not fully functional
14    // See the PubNub Rust SDK documentation for complete implementation details
15    // ...
16}
17

18fn init_pubnub() -> Result<PubNubClient<MinimalTransport>, PubNubError> {
19    // Create a transport instance
20    let transport = MinimalTransport;
21    
22    // Set up PubNub with minimal configuration
23    let pubnub = PubNubClientBuilder::with_transport(transport)
24        .with_keyset(Keyset {
25            subscribe_key: "demo",      // Replace with your subscribe key
26            publish_key: Some("demo"),  // Replace with your publish key
27            secret_key: None,
28        })
29        .with_user_id("rust-embedded-device")
30        .build()?;
31    
32    Ok(pubnub)
33}
34

35// In your main function or initialization code
36fn main() -> Result<(), PubNubError> {
37    let pubnub = init_pubnub()?;
38    
39    // Your embedded application code
40    
41    Ok(())
42}

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Conceptual example

The embedded example above is conceptual. For an actual implementation, you'll need to create a custom transport layer that implements the Transport trait for your specific environment.

For more information, refer to the Configuration section of the SDK documentation.

Set up event listeners

Listeners help your app react to events and messages. You can implement custom app logic to respond to each type of message or event.

Server-side applications

Using Rust's async streams makes it easy to process events as they arrive:

1// Import required event handling traits
2use pubnub::dx::subscribe::Update;
3use pubnub::subscribe::{Subscriber, EventSubscriber};
4use futures::StreamExt;
5

6// Listen for client status changes
7tokio::spawn(pubnub.status_stream().for_each(|status| async move {
8    println!("\nStatus: {:?}", status)
9}));
10

11// Listen for all subscription events
12tokio::spawn(subscription.stream().for_each(|event| async move {
13    match event {
14        Update::Message(message) | Update::Signal(message) => {
15            // Process incoming messages
16            if let Ok(utf8_message) = String::from_utf8(message.data.clone()) {
17                if let Ok(cleaned) = serde_json::from_str::<String>(&utf8_message) {
18                    println!("Message received: {}", cleaned);
19                }
20            }
21        }
22        Update::Presence(presence) => {
23            println!("Presence event: {:?}", presence)
24        }
25        Update::AppContext(object) => {
26            println!("Object update: {:?}", object)
27        }
28        Update::MessageAction(action) => {
29            println!("Message action: {:?}", action)
30        }
31        Update::File(file) => {
32            println!("File received: {:?}", file)
33        }
34    }
35}));

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If you only want to listen for specific events, you can use specialized streams:

1// Only listen for message events on a specific channel
2tokio::spawn(
3    channel_subscription
4        .messages_stream()
5        .for_each(|message| async move {
6            if let Ok(utf8_message) = String::from_utf8(message.data.clone()) {
7                if let Ok(cleaned) = serde_json::from_str::<String>(&utf8_message) {
8                    println!("Message received: {}", cleaned);
9                }
10            }
11        })
12);

Embedded systems

For embedded systems, you might want to use a more compact approach to event handling:

1// Use a more compact approach for resource-constrained environments
2tokio::spawn(subscription.messages_stream().for_each(|message| async move {
3    // Only process the specific fields needed rather than the entire message
4    if let Ok(text) = String::from_utf8(message.data.clone()) {
5        // Process the message with minimal allocations
6        // ...
7    }
8}));

For more information, refer to the Event Listeners section of the SDK documentation.

Create a subscription

To receive messages sent to a particular channel, you need to subscribe to it. This setup allows you to receive real-time updates whenever anyone publishes to that channel.

Server-side applications

Create a subscription to one or more channels using the subscription parameters:

1use pubnub::subscribe::SubscriptionParams;
2

3// Subscribe to a single channel
4let subscription = pubnub.subscription(SubscriptionParams {
5    channels: Some(&["my_channel"]),
6    channel_groups: None,
7    options: None
8});
9

10// Or create a subscription from a channel entity
11let channel = pubnub.channel("my_channel");
12let channel_subscription = channel.subscription(None);
13

14// Activate the subscriptions
15subscription.subscribe();
16channel_subscription.subscribe();
17

18println!("Subscribed to channels");

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For more information, refer to the Subscribe section of the SDK documentation.

Embedded systems

For embedded systems, you might want to be more careful with resource usage:

1// Create a minimal subscription with only required features
2let channel = pubnub.channel("my_channel");
3let subscription = channel.subscription(None);
4subscription.subscribe();
5

6// For very constrained systems, you might want to use specific options
7// to limit resource usage

Publish messages

When you publish a message to a channel, PubNub delivers that message to everyone who is subscribed to that channel. A message can be any type of JavaScript Object Notation (JSON)-serializable data smaller than 32 KiB.

Server-side applications

Let's publish a message to our channel:

1// Wait a moment for the subscription to establish
2tokio::time::sleep(tokio::time::Duration::from_secs(2)).await;
3

4// Send a message to the channel
5match pubnub
6    .publish_message("hello world!")
7    .channel("my_channel")
8    .r#type("text-message")  // Optional: specify a message type
9    .execute()
10    .await {
11        Ok(result) => {
12            println!("Message published successfully! Timetoken: {}", result.timetoken);
13        }
14        Err(err) => {
15            println!("Failed to publish message: {:?}", err);
16        }
17}

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Embedded systems

For embedded systems, you might want to minimize memory usage during publishing:

1// Create a simple message with minimal allocations
2let message = r#"{"text":"Hello from embedded device"}"#;
3

4// Publish the message with minimal overhead
5let result = pubnub.publish_message(message)
6    .channel("my_channel")
7    .store(false) // Don't store the message to save bandwidth
8    .execute()
9    .await;
10

11// Process the result with minimal allocations
12match result {
13    Ok(publish_result) => {
14        // Message was published successfully
15        // Process the timetoken if needed
16        let _timetoken = publish_result.timetoken;
17    }
18    Err(err) => {
19        // Handle error
20        // Log error or retry based on error type
21        if let PubNubError::TransportError(_) = err {
22            // Network error, might want to retry
23        }
24    }
25}

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Clean up resources

When your application is shutting down or a component using PubNub is being removed, it's important to properly clean up resources to avoid memory leaks and ensure network connections are closed gracefully.

Server-side applications

To properly clean up resources, unsubscribe from channels and remove listeners:

1// Unsubscribe from the channel
2subscription.unsubscribe();
3

4// Remove listeners to avoid memory leaks
5pubnub.remove_all_listeners();
6

7// For more thorough cleanup, you can also destroy the client
8// which will unsubscribe from all channels and remove all listeners
9pubnub.destroy();
10

11println!("Cleaned up PubNub resources");

This is particularly important in long-running applications that may create and dispose of multiple PubNub clients or subscriptions.

Embedded systems

For embedded systems, proper cleanup is even more critical due to limited resources:

1// Unsubscribe from channels to stop receiving messages
2subscription.unsubscribe();
3

4// Clean up resources
5pubnub.remove_all_listeners();
6pubnub.destroy();

In memory-constrained environments, make sure to clean up as soon as you're done with a resource to free memory.

Run the app

Server-side applications

To run your application:

1. Make sure all the code is in your main.rs file.
2. Run it with cargo run in your terminal.

If you're using async code, make sure your Cargo.toml includes tokio:

1[dependencies]
2pubnub = "0.6.0"
3serde = "1.0"
4serde_json = "1.0"
5tokio = { version = "1", features = ["full"] }

And your main function should have the tokio runtime attribute:

1#[tokio::main]
2async fn main() -> Result<(), Box<dyn std::error::Error>> {
3    // Your code here
4    Ok(())
5}

Embedded systems

For embedded systems, the process will depend on your specific target:

1. Configure your build for your target architecture

2. If using no_std, ensure you've properly set up your Cargo.toml:

   1[dependencies]
   2pubnub = { version = "0.6.0", default-features = false, features = ["serde", "publish"] }
   3# Add other dependencies specific to your embedded target

3. Build with cargo build --target your-target-triple

4. Flash to your device using the appropriate tools for your platform

When you run the application, you should see output similar to the following:

1PubNub client initialized successfully!
2Subscribed to channel: my_channel
3Connected to PubNub network
4Message published successfully! Timetoken: 16967543908123456
5Received message on channel 'my_channel': {"text":"Hello, world!","sender":"Rust Server"}
6Global listener: Received message on channel 'my_channel': {"text":"Hello, world!","sender":"Rust Server"}

Complete example

Here's the complete working example that puts everything together:

1use pubnub::subscribe::Subscriber;
2use futures::StreamExt;
3use tokio::time::sleep;
4use std::time::Duration;
5use serde_json;
6use pubnub::{
7    dx::subscribe::Update,
8    subscribe::{EventSubscriber, EventEmitter, SubscriptionParams},
9    Keyset, PubNubClientBuilder,
10};
11

12#[tokio::main]
13async fn main() -> Result<(), Box<dyn std::error::Error>> {
14    // Set up PubNub configuration
15    let publish_key = "demo";  // Replace with your publish key
16    let subscribe_key = "demo"; // Replace with your subscribe key
17    
18    let pubnub = PubNubClientBuilder::with_reqwest_transport()
19        .with_keyset(Keyset {
20            subscribe_key,
21            publish_key: Some(publish_key),
22            secret_key: None,
23        })
24        .with_user_id("rust-server-user")
25        .build()?;
26

27    println!("PubNub client initialized successfully!");
28

29    // Create a subscription to a channel
30    let subscription = pubnub.subscription(SubscriptionParams {
31        channels: Some(&["my_channel"]),
32        channel_groups: None,
33        options: None
34    });
35

36    // Create another subscription using a channel entity
37    let channel_entity = pubnub.channel("my_channel_2");
38    let channel_entity_subscription = channel_entity.subscription(None);
39

40    // Activate the subscriptions
41    subscription.subscribe();
42    channel_entity_subscription.subscribe();
43

44    println!("Subscribed to channels");
45

46    // Listen for client status changes
47    tokio::spawn(pubnub.status_stream().for_each(|status| async move {
48        println!("\nStatus: {:?}", status)
49    }));
50    
51    // Listen for all types of events
52    tokio::spawn(subscription.stream().for_each(|event| async move {
53        match event {
54            Update::Message(message) | Update::Signal(message) => {
55                // Process incoming messages
56                if let Ok(utf8_message) = String::from_utf8(message.data.clone()) {
57                    if let Ok(cleaned) = serde_json::from_str::<String>(&utf8_message) {
58                        println!("Message received: {}", cleaned);
59                    }
60                }
61            }
62            Update::Presence(presence) => {
63                println!("Presence event: {:?}", presence)
64            }
65            Update::AppContext(object) => {
66                println!("Object update: {:?}", object)
67            }
68            Update::MessageAction(action) => {
69                println!("Message action: {:?}", action)
70            }
71            Update::File(file) => {
72                println!("File received: {:?}", file)
73            }
74        }
75    }));
76

77    // Only listen for message events on the second channel
78    tokio::spawn(
79        channel_entity_subscription
80            .messages_stream()
81            .for_each(|message| async move {
82                if let Ok(utf8_message) = String::from_utf8(message.data.clone()) {
83                    if let Ok(cleaned) = serde_json::from_str::<String>(&utf8_message) {
84                        println!("Message received on channel 2: {}", cleaned);
85                    }
86                }
87            }),
88    );
89

90    // Wait a moment for the subscriptions to establish
91    sleep(Duration::from_secs(2)).await;
92

93    // Send a message to the first channel
94    pubnub
95        .publish_message("hello world!")
96        .channel("my_channel")
97        .r#type("text-message")
98        .execute()
99        .await?;
100

101    // Send a message to the second channel
102    pubnub
103        .publish_message("hello world on the other channel!")
104        .channel("my_channel_2")
105        .r#type("text-message")
106        .execute()
107        .await?;
108

109    // Keep the program running to receive the published messages
110    sleep(Duration::from_secs(15)).await;
111

112    // Clean up resources (uncomment if needed for your use case)
113    // subscription.unsubscribe();
114    // channel_entity_subscription.unsubscribe();
115

116    Ok(())
117}

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Troubleshooting

If you don't see the expected output, here are some common issues and how to fix them:

Issue	Possible Solutions
No connection message	Check your internet connection. Verify your publish and subscribe keys are correct. Make sure you're not behind a firewall blocking PubNub's connections.
Message not received	Double-check that you're subscribed to the correct channel. Verify that the message was actually sent (check for any error messages). Make sure you're waiting long enough for the message to be delivered.
Build errors	Ensure you've added the PubNub dependency correctly. Check that you're using a compatible version of Rust (1.65.0+ is recommended). Make sure all imports are correct.
Runtime errors	If using async code, ensure you've set up the tokio runtime correctly. Make sure you're handling errors properly with proper match statements or the ? operator.

Next steps

Great job! 🎉 You've successfully created your first PubNub application with Rust. Here are some exciting things you can explore next:

Advanced features

• Try out Presence to track online/offline status.
• Use Access Manager to secure your channels.
• Explore message encryption with the built-in CryptoModule.

Real examples

• Look at the examples folder in the repository.
• Explore our GitHub repository for more code samples.

More help

• Check out our SDK reference documentation for detailed API information.
• Join our Discord community to connect with other developers.
• Visit our support portal for additional resources.
• Ask our AI assistant (the looking glass icon at the top of the page) for help.