TON Connect Integration for Mobile Wallets: Solving SSE, Deeplink & Transaction Signing

Integrating TON Connect into a mobile wallet presents several key challenges: establishing a secure channel between the dApp and the wallet, correctly serializing cryptographic data, and choosing the optimal transport. On one project, the bridge server disconnected every 30 minutes due to SSE timeout, forcing us to implement automatic reconnection with exponential backoff. TON Connect is a communication protocol over HTTP bridge with push notifications via SSE. Unlike WalletConnect (EVM world), it uses its own protocol, requiring deep understanding of the transport layer and cryptography. We have successfully integrated TON Connect into wallets with over 100,000 users, tested compatibility with 30+ dApps, and ensure connection stability at 99.9%. Such integration reduces maintenance costs and accelerates time to market, paying off within an average of half a year.

How TON Connect Transport Works

The protocol operates through a bridge server (bridge.tonapi.io or a self-hosted one). The wallet and dApp exchange encrypted messages via this bridge — no direct connection. Encryption uses NaCl box (X25519 + XSalsa20-Poly1305).

The mobile wallet app connects to the bridge via SSE (Server-Sent Events): GET /bridge/{clientId}/events. This is a long-lived HTTP request that keeps the connection open. On iOS, this is problematic: URLSession does not natively support SSE, requiring an EventSource library or a custom implementation via URLSessionDataDelegate. On Android with OkHttp, there is no built-in SSE support either, but the EventSource from the OkHttp team (com.squareup.okhttp3:okhttp-sse) solves the problem.

An alternative transport is deeplink. The dApp encodes a tc:// or https://ton.app/... link; the user clicks it, the wallet opens and receives a connect request from URL parameters. This is a synchronous flow without a bridge — simpler, but requires the dApp and wallet to be on the same device.

Why ton_proof is Critical for Security

ton_proof is a cryptographic proof of wallet ownership without signing a transaction. Format: ton-proof-item-v2/<wc>:<addr_bytes>/<app_domain>/<timestamp>/<payload>. It is signed with the wallet's private key via Ed25519. The dApp verifies the signature via TON API, not trusting the wallet blindly. The TON Connect specification mandates using the raw address for addr_bytes; otherwise the signature will be invalid.

A typical mistake in implementing ton_proof: incorrect serialization of addr_bytes — the raw format is needed (workchain + 32-byte hash), not the user-friendly bounce/non-bounce address. Check the specification. ton_proof allows the dApp to confirm that the user actually owns the wallet without signing a full transaction. The mechanism prevents replay attacks by including the domain and timestamp.

Handling Connect Request in the Wallet

When receiving a connection request, the wallet must:

1. Decode the ConnectRequest from the encrypted payload (or from the deeplink r parameter).
2. Show the user: which dApp is requesting connection, which items are needed (ton_addr, ton_proof).
3. Obtain user approval.
4. Form a ConnectResponse with the wallet address, network (mainnet/testnet), public key, and ton_proof if requested.

Transaction Signing and BOC Decoding

After connection, the dApp sends a SendTransactionRequest with a BOC (Bag of Cells) — the binary representation of a TON transaction. The wallet:

1. Decodes the BOC using ton-core or @ton/ton.
2. Shows transaction details to the user: recipient, amount, comment.
3. Signs the transaction with the private key.
4. Sends the signed BOC to the TON network via tonapi.io or toncenter.com.
5. Returns a SendTransactionResponse with the transaction hash to the dApp.

How to Decode BOC?

Decoding a BOC for UI display is non-trivial. The BOC may contain smart contract calls with arbitrary payloads. For standard jetton transfers, there is an OP code parser (0xf8a7ea5 — jetton transfer); for the rest, we show raw hex with a warning. Use ton-core libraries for parsing.

What's Included in TON Connect Integration

The scope of work includes:

• Audit of the current wallet architecture and integration recommendations.
• Documentation of the protocol and bridge server configuration.
• Implementation of the chosen transport (SSE, deeplink, or both).
• Codebase for the TON Connect module in Swift/Kotlin/Dart/TypeScript.
• Testing with 5+ real dApps (Tonkeeper, Getgems, etc.).
• Writing unit and integration tests.
• Training the client's team.
• Support for one month after release.

TON Connect Integration Stages

1. Analysis — study your wallet architecture, select transport, agree on specifics.
2. Design — develop connection schema, define ton_proof and BOC processing.
3. Implementation — code in Swift/Kotlin/Flutter with App Store and Google Play requirements. Implement push support (APNs/FCM).
4. Testing — verify with real dApps, validate transaction signatures.
5. Deployment — publish the update in stores, configure bridge (if needed).

TON Connect vs WalletConnect

TON Connect is better than WalletConnect in the TON ecosystem due to native integration with TON Blockchain: no data type conversion needed, and ton_proof is more secure than message signing. Also, SSE support allows the wallet to receive balance update events without additional requests. If you need integration with dApps in TON, TON Connect is the only corporate standard. Implementation is available on iOS (Swift), Android (Kotlin), and cross-platform frameworks. For native platforms, the SDK is developed in-house per specification, and a good reference is the Tonkeeper open-source repository.

Timeline and Cost

Integration of TON Connect into an existing wallet (connection and transaction signing only) — 3–5 weeks. A full TON wallet from scratch (seed management, key derivation, jetton support, NFT, staking) — from 4 to 6 months. Cost is calculated individually after analyzing your project.

Estimate your project: contact us for a consultation. Order TON Connect integration for your wallet — get a stable solution with a guarantee.

How to Start Integrating API into a Mobile App?

The request goes out, the response doesn't come, timeout — 30 seconds. The user stares at the spinner. No network — mobile card in the subway. Or the network is there, but the server returns 200 with an HTML error page instead of JSON — and the app crashes on JSONDecoder.decode(). We see such cases on every second project. So integrating API into a mobile app is not just calling an endpoint, but designing a reliable network layer: error handling, caching, offline mode, certificate pinning. Order an audit of your current network layer — we will evaluate the project in 1 day. Our team guarantees a thorough analysis and provides a detailed roadmap.

Standard libraries like URLSession and OkHttp provide basic HTTP clients, but for production you need retries with exponential backoff, status code validation, typed deserialization, and network state monitoring. Without this, the app loses data and users. We have been doing mobile development for 5 years and implemented more than 30 projects with API integration on iOS, Android, and Flutter — from startups to enterprise solutions.

How to Choose a Protocol for API Integration?

REST remains the standard for most projects. But when a profile screen needs 5 fields out of 40, GraphQL eliminates over-fetching and reduces traffic by 30–60%. gRPC is justified for thousands of requests per minute (trading, IoT) — binary serialization is 3–5 times faster than JSON. WebSocket is the only choice for real-time without polling (messages, notifications).

Practical example: For a fintech app, we replaced REST (40 fields) with GraphQL — response size dropped from 12 KB to 2.5 KB, screen render time decreased by 70%. Traffic savings were significant. Our certified iOS and Android developers have deep experience with all these protocols — you can rely on proven solutions.

How to Ensure Reliable Connection and Offline-First?

Users lose network in the subway, elevator, tunnel. A mobile app must work without internet — at least in read-only mode. We implement the offline-first pattern:

1. On screen open, first show data from the local cache (Core Data / Room).
2. Simultaneously perform a network request, update UI after response.
3. If network is unavailable — show cached data and a 'no connection' label.
4. When network is restored, automatically synchronize changes.

For HTTP response caching we use URLCache (iOS) and OkHttp Cache (Android) with Cache-Control support. For structured data — SwiftData / Room. NWPathMonitor / ConnectivityManager.NetworkCallback monitor network state and trigger updates.

REST and Client Library Selection

Alamofire (iOS) — de facto standard for Swift projects. On top of URLSession it adds request chaining, response validation, automatic retry, certificate pinning via ServerTrustManager. AF.request() with .validate() returns an error for any status code outside 200–299. Without .validate(), Alamofire considers 404 and 500 as successful responses. With Swift Concurrency — async version via serializingDecodable.

Retrofit (Android) — annotation-based HTTP client on top of OkHttp. An interface with annotations compiles into implementation. @GET, @POST, @Path, @Query, @Body — declarative API description. OkHttp under the hood: connection pooling, transparent gzip, HTTP/2 multiplex. HttpLoggingInterceptor — logging in debug builds. Authenticator — automatic token refresh on 401.

Ktor (KMM/Flutter) — multiplatform HTTP client. On iOS it works via Darwin engine (URLSession), on Android — via OkHttp. Single code for both platforms with KMM architecture.

GraphQL: When REST Falls Short

REST returns a fixed structure. A profile screen needs name, avatar, email — the server sends 40 fields. Over-fetching. GraphQL solves this: the client requests exactly the needed fields. This is critical for mobile where traffic and parsing time are real constraints. Apollo iOS and Apollo Kotlin generate typed classes from schema: schema.graphql + query files → strict types at compile time. Subscriptions via WebSocket — real-time without polling. Limitation: GraphQL is harder to cache at the HTTP level. Apollo uses a normalized in-memory cache InMemoryNormalizedCache — requests with overlapping data update the cache without duplication.

WebSocket: Real-Time Without Extra Traffic

Polling (setInterval every 5 seconds) — battery and traffic waste. WebSocket is a persistent bidirectional connection. iOS: URLSessionWebSocketTask (native, iOS 13+). Android: OkHttp WebSocket. Mandatory reconnect handling: on onFailure — exponential backoff (1s → 2s → 4s → 8s → max 60s). Socket.IO is an overlay with automatic reconnect, but for new projects native WebSocket is preferable (fewer dependencies).

gRPC: For High-Load Services

gRPC with protobuf — binary serialization: smaller size, faster parsing. grpc-swift for iOS, grpc-kotlin for Android. The protobuf schema compiles to typed classes. Streaming (server-side, client-side, bidirectional) is a native feature. Application threshold: high request frequency (trading, IoT) or critical latency. For regular CRUD, REST is simpler to debug and monitor.

Certificate Pinning and Security

A corporate proxy can intercept HTTPS by substituting the certificate. Certificate pinning prevents this: the app accepts only a specific certificate or public key. Alamofire: ServerTrustManager with PinnedCertificatesTrustEvaluator. OkHttp: CertificatePinner with SHA-256 hash. Apple's App Transport Security documentation recommends pinning certificates for sensitive data. Operational complexity: on certificate rotation, older app versions stop working. Solution — pinning to the CA public key or support multiple pins with a grace period.

What Is Included in the Work

We deliver: source code of the network layer, documentation on used libraries, certificate rotation instructions, 2 weeks post-delivery support. Our experience guarantees that the solution will be stable and maintainable.

Timeline and Cost

Implementation of a network layer with REST, retry, caching, and offline mode — 1–2 weeks. Adding GraphQL or WebSocket — another 1–2 weeks. gRPC — 2–3 weeks, including code generation. The cost is calculated individually after analyzing the API and offline behavior requirements. We will evaluate the project in 1 day — contact us for a consultation. Get a reliable API integration with guaranteed quality.