Function build_host

src/websockets/headers.py:39–65

Build a ``Host`` header.

(
    host: str,
    port: int,
    secure: bool,
    *,
    always_include_port: bool = False,
)

def build_host(
    host: str,
    port: int,
    secure: bool,
    *,
    always_include_port: bool = False,
) -> str:
    """
    Build a ``Host`` header.

    """
    # https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
    # IPv6 addresses must be enclosed in brackets.
    try:
        address = ipaddress.ip_address(host)
    except ValueError:
        # host is a hostname
        pass
    else:
        # host is an IP address
        if address.version == 6:
            host = f"[{host}]"

    if always_include_port or port != (443 if secure else 80):
        host = f"{host}:{port}"

    return host


# To avoid a dependency on a parsing library, we implement manually the ABNF