microsoft/aspire · error · ArgumentOutOfRangeException

Port range end must be between

Error message

Port range end must be between {MinPort} and {MaxPort}.

What it means

Thrown by PortRange.ValidateRange when the range end falls outside the valid port interval [MinPort, MaxPort]. Raised as ArgumentOutOfRangeException naming the end parameter, mirroring the start validation.

Solutions

1. Set range end to a value between 1 and 65535 inclusive.
2. Ensure the end is computed as start + size - 1 with a positive size, then clamped to 65535.
3. Validate the configured range with IsValidPort before calling APIs that take a range.

Example fix

// before
PortRange.ValidateRange(8000, 0, nameof(start), nameof(end));
// after
PortRange.ValidateRange(8000, 8100, nameof(start), nameof(end));

if (end is < 1 or > 65535)
    throw new ArgumentException($"Port range end {end} must be between 1 and 65535.");

try { PortRange.ValidateRange(start, end, nameof(start), nameof(end)); }
catch (ArgumentOutOfRangeException ex) when (ex.ParamName == nameof(end)) { /* fix configured end */ }

When it happens

Trigger: Calling ValidateRange with a rangeEnd < 1 or > 65535, e.g. ValidateRange(8000, 0) or ValidateRange(8000, 70000).

Common situations: Hand-edited port range configuration with an invalid upper bound; computing the end as start+size where size overflowed or was 0/negative leading to an invalid end.

Understand the failure class

Background: "value must be between 0 and 1" / "out of range" / "must not be negative" errors: fixing range-validation failures across open-source libraries — this error's family across 42 libraries.

Related errors

• Port range start must be between
• Invalid value " " for " ". Expected a port range formatted…
• Port range start must be less than or equal to the range…
• Random walk offset must be within the configured range size.
• Tunnel expiration must be from 1 hour through 30 days.

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/d3f7913bfa0df969. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting/Dcp/PortRange.cs:43

    public static bool IsValidPort(int port)
    {
        return port is >= MinPort and <= MaxPort;
    }

    /// <summary>
    /// Validates that <paramref name="rangeStart"/> and <paramref name="rangeEnd"/> form a valid,
    /// non-empty, ordered port range, throwing if not.
    /// </summary>
    public static void ValidateRange(int rangeStart, int rangeEnd, string rangeStartParamName, string rangeEndParamName)
    {
        if (!IsValidPort(rangeStart))
        {
            throw new ArgumentOutOfRangeException(rangeStartParamName, rangeStart, $"Port range start must be between {MinPort} and {MaxPort}.");
        }

        if (!IsValidPort(rangeEnd))
        {
            throw new ArgumentOutOfRangeException(rangeEndParamName, rangeEnd, $"Port range end must be between {MinPort} and {MaxPort}.");
        }

        if (rangeStart > rangeEnd)
        {
            throw new ArgumentException("Port range start must be less than or equal to the range end.", rangeStartParamName);
        }
    }
}

View on GitHub (pinned to 25830f84bd)