input: String,
      pos: Int,
      limit: Int,
    ): Int =
      try {
        // Canonicalize the port string to skip '\n' etc.
        val portString = input.canonicalize(pos = pos, limit = limit, encodeSet = "")
        val i = portString.toInt()
        if (i in 1..65535) i else -1
      } catch (_: NumberFormatException) {
        -1 // Invalid port.
      }
  }

  companion object {