C# sockets, HttpClient and RestSharp

Integration · Sockets · Messages · Official networking research

Program.cs uses URnetwork.SDK with a local Device. UrStream.cs adapts its Conn to a .NET Stream and UrSession.cs owns the native SDK handles.

Install and run

Use .NET 8+:

dotnet add package URnetwork.SDK --version <socket-release-version>
dotnet run -- --version
dotnet run -- --new-id
dotnet run -- https://example.com/
dotnet run -- restsharp https://example.com/
dotnet run -- udp echo.example:9000
dotnet run -- dtls dtls.example:9001

Before first publication, build sdk/csharp, then restore with dotnet restore --source /path/to/sdk/csharp/dist/artifacts --source https://api.nuget.org/v3/index.json. The project accepts -p:UrSdkVersion= and defaults to the local development package. Set the Device variables below before live requests.

Replace the HTTP socket factory

The HTTP handler receives the unresolved DnsEndPoint and passes its hostname to the Device. TLS, SNI, certificate checks and HTTP negotiation remain in HttpClient, layered on that stream. HTTP/2-or-lower is selected: HTTP/3 uses QUIC and cannot be intercepted through this stream callback.

The async facade offloads the blocking C ABI call, owns the read buffer until it completes, and closes the connection on cancellation. A connection returned after canceled establishment is also disposed. This is suitable for the example; very large numbers of concurrent blocking calls need worker-pool sizing or a dedicated async bridge. Partial data is delivered before a deferred read error.

Sources checked September 14, 2026: .NET ConnectCallback, HttpVersionPolicy, RestSharp custom HttpClient.

Device setup

The executable creates a local Device with the scoped client JWT issued by your service backend and chooses the best available location. Follow the integration guide: the JWT must contain its assigned client_id; only the backend holds the root JWT. Generate an instance ID once with this program's --new-id mode, save it, and reuse it for this installation.

export URNETWORK_CLIENT_JWT='your-scoped-client-jwt'
export URNETWORK_INSTANCE_ID='your-persisted-instance-uuid'

Keep the network-space manager alive until the Device closes. The sample owns and releases these objects in that order. HTTP proxy modes use the Go proxy's Device instead.

Socket behavior

The destination connection lives in the SDK's user-space network stack and sends packets through the Device's URnetwork connection. It is not a kernel socket: its handle cannot be passed to select, poll, an OS socket option, or a library that requires a native file descriptor. Creating these application sockets does not require installing a system VPN or opening a kernel TUN device.

Pass the hostname unchanged with tcp or udp. The SDK resolves A and AAAA records through its connection and applies Happy Eyeballs; use tcp4/tcp6 or udp4/udp6 to force a family. Plain UDP races the initial application datagram and selects the address that sends the first reply. That initial datagram can be delivered to both addresses. Subsequent writes use the winner; a silent server cannot select a winner, so set a read/write deadline. Use an echo server you control for UDP examples. An empty datagram is data, not stream EOF.

TLS verifies the certificate and destination hostname. TLS-over-TCP and DTLS-over-UDP use the same Device packet path. DTLS needs a DTLS server, not a plain UDP echo server. Deadlines are absolute Unix milliseconds in portable bindings; zero clears them. Close each connection and then its Device. Listener/server sockets are a future API.

These are application integration examples. The core SDK suite separately tests real TCP/UDP packets, IPv4/IPv6, hostname races, TLS/DTLS, deadlines, close, and local/RPC transport behavior. A version/self-test command checks installation without using account credentials; live examples require a working account and provider path.