What does it do, what technologies and concepts are used and how does it reach its goal. Step by step by step, divide these contents into smaller parts and explain.A fast TCP/UDP tunnel over HTTP

Chisel is a fast TCP/UDP tunnel, transported over HTTP, secured via SSH. Single executable including both client and server. Written in Go (golang). Chisel is mainly useful for passing through firewalls, though it can also be used to provide a secure endpoint into your network.

Easy to use
Performant*
Encrypted connections using the SSH protocol (via crypto/ssh)
Authenticated connections; authenticated client connections with a users config file, authenticated server connections with fingerprint matching.
Client auto-reconnects with exponential backoff
Clients can create multiple tunnel endpoints over one TCP connection
Clients can optionally pass through SOCKS or HTTP CONNECT proxies
Reverse port forwarding (Connections go through the server and out the client)
Server optionally doubles as a reverse proxy
Server optionally allows SOCKS5 connections (See guide below)
Clients optionally allow SOCKS5 connections from a reversed port forward
Client connections over stdio which supports ssh -o ProxyCommand providing SSH over HTTP

$ chisel --help

  Usage: chisel [command] [--help]

  Version: X.Y.Z

  Commands:
    server - runs chisel in server mode
    client - runs chisel in client mode

  Read more:
    https://github.com/jpillora/chisel
$ chisel server --help

  Usage: chisel server [options]

  Options:

    --host, Defines the HTTP listening host – the network interface
    (defaults the environment variable HOST and falls back to 0.0.0.0).

    --port, -p, Defines the HTTP listening port (defaults to the environment
    variable PORT and fallsback to port 8080).

    --key, (deprecated use --keygen and --keyfile instead)
    An optional string to seed the generation of a ECDSA public
    and private key pair. All communications will be secured using this
    key pair. Share the subsequent fingerprint with clients to enable detection
    of man-in-the-middle attacks (defaults to the CHISEL_KEY environment
    variable, otherwise a new key is generate each run).

    --keygen, A path to write a newly generated PEM-encoded SSH private key file.
    If users depend on your --key fingerprint, you may also include your --key to
    output your existing key. Use - (dash) to output the generated key to stdout.

    --keyfile, An optional path to a PEM-encoded SSH private key. When
    this flag is set, the --key option is ignored, and the provided private key
    is used to secure all communications. (defaults to the CHISEL_KEY_FILE
    environment variable). Since ECDSA keys are short, you may also set keyfile
    to an inline base64 private key (e.g. chisel server --keygen - | base64).

    --authfile, An optional path to a users.json file. This file should
    be an object with users defined like:
      {
        "<user:pass>": ["<addr-regex>","<addr-regex>"]
      }
    when <user> connects, their <pass> will be verified and then
    each of the remote addresses will be compared against the list
    of address regular expressions for a match. Addresses will
    always come in the form "<remote-host>:<remote-port>" for normal remotes
    and "R:<local-interface>:<local-port>" for reverse port forwarding
    remotes. This file will be automatically reloaded on change.

    --auth, An optional string representing a single user with full
    access, in the form of <user:pass>. It is equivalent to creating an
    authfile with {"<user:pass>": [""]}. If unset, it will use the
    environment variable AUTH.

    --keepalive, An optional keepalive interval. Since the underlying
    transport is HTTP, in many instances we'll be traversing through
    proxies, often these proxies will close idle connections. You must
    specify a time with a unit, for example '5s' or '2m'. Defaults
    to '25s' (set to 0s to disable).

    --backend, Specifies another HTTP server to proxy requests to when
    chisel receives a normal HTTP request. Useful for hiding chisel in
    plain sight.

    --socks5, Allow clients to access the internal SOCKS5 proxy. See
    chisel client --help for more information.

    --reverse, Allow clients to specify reverse port forwarding remotes
    in addition to normal remotes.

    --tls-key, Enables TLS and provides optional path to a PEM-encoded
    TLS private key. When this flag is set, you must also set --tls-cert,
    and you cannot set --tls-domain.

    --tls-cert, Enables TLS and provides optional path to a PEM-encoded
    TLS certificate. When this flag is set, you must also set --tls-key,
    and you cannot set --tls-domain.

    --tls-domain, Enables TLS and automatically acquires a TLS key and
    certificate using LetsEncrypt. Setting --tls-domain requires port 443.
    You may specify multiple --tls-domain flags to serve multiple domains.
    The resulting files are cached in the "$HOME/.cache/chisel" directory.
    You can modify this path by setting the CHISEL_LE_CACHE variable,
    or disable caching by setting this variable to "-". You can optionally
    provide a certificate notification email by setting CHISEL_LE_EMAIL.

    --tls-ca, a path to a PEM encoded CA certificate bundle or a directory
    holding multiple PEM encode CA certificate bundle files, which is used to 
    validate client connections. The provided CA certificates will be used 
    instead of the system roots. This is commonly used to implement mutual-TLS. 

    --pid Generate pid file in current working directory

    -v, Enable verbose logging

    --help, This help text

  Signals:
    The chisel process is listening for:
      a SIGUSR2 to print process stats, and
      a SIGHUP to short-circuit the client reconnect timer

  Version:
    X.Y.Z

  Read more:
    https://github.com/jpillora/chisel