sgl-project/sglang · error · ValueError

Missing port in address (expected host:port): {addr!r}

Error message

Missing port in address (expected host:port): {addr!r}

What it means

NetworkAddress.parse was given a string with no ':' at all and not starting with '[', so no port can be extracted. Every address passed to parse must be in host:port (or [ipv6]:port) form.

Source

Thrown at python/sglang/srt/utils/network.py:545

        # --- Bracketed IPv6: [addr]:port ---
        if addr.startswith("["):
            close = addr.find("]")
            if close == -1:
                raise ValueError(f"Missing closing bracket in IPv6 address: {addr!r}")
            host = addr[1:close]
            if not _is_ipv6(host):
                raise ValueError(f"Invalid IPv6 address inside brackets: {host!r}")
            rest = addr[close + 1 :]
            if not rest.startswith(":") or len(rest) < 2:
                raise ValueError(
                    f"Expected ':port' after closing bracket, got: {rest!r}"
                )
            return NetworkAddress(host, _parse_port(rest[1:]))

        # --- Plain host:port (IPv4 / hostname) ---
        if ":" not in addr:
            raise ValueError(f"Missing port in address (expected host:port): {addr!r}")
        host, port_str = addr.rsplit(":", 1)
        if not host:
            raise ValueError(f"Empty host in address: {addr!r}")
        # Guard against bare IPv6 slipping through
        if ":" in host and _is_ipv6(host):
            raise ValueError(
                f"Bare IPv6 address without brackets is ambiguous: {addr!r}. "
                f"Use [{host}]:{port_str} instead."
            )
        return NetworkAddress(host, _parse_port(port_str))

    def __str__(self) -> str:
        return self.to_host_port_str()

    def __repr__(self) -> str:
        return f"NetworkAddress({self.host!r}, {self.port})"

View on GitHub (pinned to 0132848349)

Solutions

  1. Append the port: 'localhost:8080'
  2. Fix the code that assembles the address to always join host and port
  3. Default the port at the call site if a bare host is legitimately allowed

Example fix

# before
addr = NetworkAddress.parse(host)  # host == 'worker-0'
# after
addr = NetworkAddress.parse(f'{host}:{port}')
Defensive patterns

Strategy: validation

Validate before calling

def has_host_and_port(addr: str) -> bool:
    return bool(addr) and not addr.startswith('[') and ':' in addr

Type guard

null

Try / catch

try:
    NetworkAddress.parse(addr)
except ValueError as e:
    if 'Missing port' in str(e):
        addr = f'{addr}:{DEFAULT_PORT}'

Prevention

When it happens

Trigger: NetworkAddress.parse('localhost'), '10.0.0.1', or a bare IPv6 without brackets like '::1' (no brackets means the ':' check path differs, but pure hostnames hit this).

Common situations: Passing a hostname where a host:port pair is expected — e.g. --host without --port concatenated, or reading a host-only env var into an address field.

Related errors

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/59c46bce5382e700. Report an issue: GitHub.