A modern, simple TCP tunnel in Rust that exposes local ports to a remote server, bypassing standard NAT connection firewalls. That's all it does: no more, and no less.
# Installation (requires Rust, see alternatives below) cargo install bore-cli # On your local machine bore local 8000 --to bore.pub
This will expose your local port at
localhost:8000 to the public internet at
bore.pub:<PORT>, where the port number is assigned randomly.
Similar to localtunnel and ngrok, except
bore is intended to be a highly efficient, unopinionated tool for forwarding TCP traffic that is simple to install and easy to self-host, with no frills attached.
bore totals about 400 lines of safe, async Rust code and is trivial to set up — just run a single binary for the client and server.)
If you're on macOS,
bore is packaged as a Homebrew core formula.
brew install bore-cli
Otherwise, the easiest way to install bore is from prebuilt binaries. These are available on the releases page for macOS, Windows, and Linux. Just unzip the appropriate file for your platform and move the
bore executable into a folder on your PATH.
You also can build
bore from source using Cargo, the Rust package manager. This command installs the
bore binary at a user-accessible path.
cargo install bore-cli
We also publish versioned Docker images for each release. The image is built for an AMD 64-bit architecture. They're tagged with the specific version and allow you to run the statically-linked
bore binary from a minimal "scratch" container.
docker run -it --init --rm --network host ekzhang/bore <ARGS>
This section describes detailed usage for the
bore CLI command.
You can forward a port on your local machine by using the
bore local command. This takes a positional argument, the local port to forward, as well as a mandatory
--to option, which specifies the address of the remote server.
bore local 5000 --to bore.pub
You can optionally pass in a
--port option to pick a specific port on the remote to expose, although the command will fail if this port is not available. Also, passing
--local-host allows you to expose a different host on your local area network besides the loopback address
The full options are shown below.
Starts a local proxy to the remote server Usage: bore local [OPTIONS] --to <TO> <LOCAL_PORT> Arguments: <LOCAL_PORT> The local port to expose Options: -l, --local-host <HOST> The local host to expose [default: localhost] -t, --to <TO> Address of the remote server to expose local ports to [env: BORE_SERVER=] -p, --port <PORT> Optional port on the remote server to select [default: 0] -s, --secret <SECRET> Optional secret for authentication [env: BORE_SECRET] -h, --help Print help information
As mentioned in the startup instructions, there is a public instance of the
bore server running at
bore.pub. However, if you want to self-host
bore on your own network, you can do so with the following command:
That's all it takes! After the server starts running at a given address, you can then update the
bore local command with option
--to <ADDRESS> to forward a local port to this remote server.
The full options for the
bore server command are shown below.
Runs the remote proxy server Usage: bore server [OPTIONS] Options: --min-port <MIN_PORT> Minimum accepted TCP port number [default: 1024] --max-port <MAX_PORT> Maximum accepted TCP port number [default: 65535] -s, --secret <SECRET> Optional secret for authentication [env: BORE_SECRET] -h, --help Print help information
There is an implicit control port at
7835, used for creating new connections on demand. At initialization, the client sends a "Hello" message to the server on the TCP control port, asking to proxy a selected remote port. The server then responds with an acknowledgement and begins listening for external TCP connections.
Whenever the server obtains a connection on the remote port, it generates a secure UUID for that connection and sends it back to the client. The client then opens a separate TCP stream to the server and sends an "Accept" message containing the UUID on that stream. The server then proxies the two connections between each other.
For correctness reasons and to avoid memory leaks, incoming connections are only stored by the server for up to 10 seconds before being discarded if the client does not accept them.
On a custom deployment of
bore server, you can optionally require a secret to prevent the server from being used by others. The protocol requires clients to verify possession of the secret on each TCP connection by answering random challenges in the form of HMAC codes. (This secret is only used for the initial handshake, and no further traffic is encrypted by default.)
# on the server bore server --secret my_secret_string # on the client bore local <LOCAL_PORT> --to <TO> --secret my_secret_string
If a secret is not present in the arguments,
bore will also attempt to read from the
BORE_SECRET environment variable.
The author would like to thank the contributors and maintainers of the Tokio project for making it possible to write ergonomic and efficient network services in Rust.