[jonathan-kosgei]

Summary

Every IPDataClient created without an HttpClient used to build its own HttpClient, so each client paid a fresh TCP + TLS handshake, and the netstandard2.0-only assembly never negotiated HTTP/2. This PR makes the library amortise the cost of HTTPS and adds the response fields the API now returns. Two commits:

1. Reuse HTTPS connections and negotiate HTTP/2

• IPData.csproj targets netstandard2.0;net8.0; System.Text.Json 4.7.2 is referenced only for netstandard2.0 (in-box on net8.0). VersionPrefix 3.0.1 → 3.1.0.
• HttpClientAdapter: default adapters share one process-wide HttpClient created lazily by CreateDefaultClient() (Lazy<HttpClient>, never disposed). On .NET 5+ it wraps a SocketsHttpHandler with PooledConnectionLifetime 5 min, PooledConnectionIdleTimeout 60 s, KeepAlivePingDelay 30 s, KeepAlivePingTimeout 15 s, KeepAlivePingPolicy.Always, UseCookies = false; on .NET Standard 2.0 an HttpClientHandler { UseCookies = false }. User-supplied HttpClient / IHttpClient instances stay user-owned. internal HttpClient Client is exposed for tests.
• IPDataClient: all eleven requests go through a private CreateRequest(HttpMethod, Uri); on .NET 5+ it sets Version = HttpVersion.Version20 and VersionPolicy = RequestVersionOrLower, so HTTP/2 is negotiated through ALPN with automatic HTTP/1.1 fallback. The netstandard2.0 asset never sets Version 2.0 (.NET Framework throws). SendRequestAsync disposes the request and the response. New additive constructor IPDataClient(string apiKey, HttpClient httpClient, Uri baseUrl).
• JsonSerializer: IgnoreNullValues is obsolete on net8.0 and is replaced there by DefaultIgnoreCondition = WhenWritingNull.
• Tests (net8.0): request version and policy asserted for GET and bulk POST through the existing Mock<IHttpClient>; a success-path test proves disposal does not break deserialisation; HttpClientAdapterTests cover the shared default client, custom-client pass-through and the handler configuration (the default client's handler is reached through reflection on HttpMessageInvoker._handler, as there is no public accessor; the helper fails with an explicit message if that field is ever renamed); the real-network test is deleted; a RecordingHttpMessageHandler drives a real HttpClient offline.
• README: new "Connection reuse and HTTP/2" section. CI: dotnet pack … --no-build smoke step so multi-TFM packaging failures surface on PRs.

2. Add is_satellite, is_anycast and dated blocklist entries

• IPLookupResult.IsSatellite / IsAnycast (bool, [JsonPropertyName("is_satellite")] / ("is_anycast")), false when the key is absent; usable as field selectors.
• BlocklistInfo.FirstSeen / LastSeen (string, YYYY-MM-DD UTC) and DaysSeen (int?), all optional.
• Threat.Blocklists setter made public. System.Text.Json never populates collection properties without a public setter, so since the Newtonsoft.Json → System.Text.Json migration the list has always deserialised empty (on master, the API's complete sample response gives Threat.Blocklists.Count == 0), and the new first_seen / last_seen / days_seen fields would have been unreachable. IPLookupResult.Languages has the identical defect but is outside the lines this change touches (see "Noticed, not changed").
• Fixtures from the three API sample responses; tests for typed values, false-when-absent, optional dates, bulk per-item shape, field-name selection and unknown-key tolerance. README "Response fields" section.

What changes for users

• Faster repeated lookups, zero configuration. new IPDataClient("API_KEY") now shares one process-wide pooled HttpClient with every other default-constructed client; consecutive lookups reuse the TCP/TLS connection instead of handshaking each time. Keep one client (or one per API key / endpoint) and reuse it for every call.
• HTTP/2 on .NET 8+. Applications on net8.0 or later get the net8.0 asset: every request asks for HTTP/2 and falls back to HTTP/1.1 automatically. .NET Framework and other .NET Standard 2.0 consumers get the netstandard2.0 asset with HTTP/1.1 keep-alive, now over a shared pool.
• Idle policy. Default pool on .NET 8+: idle connections closed after 60 s, every connection recycled after 5 min, HTTP/2 keep-alive pings every 30 s. The netstandard2.0 asset keeps the platform defaults.
• New constructor IPDataClient(string apiKey, HttpClient httpClient, Uri baseUrl) to combine your own HttpClient (for example from IHttpClientFactory) with the EU endpoint.
• Lifecycle and thread safety. Nothing to dispose: the shared default client lives for the process; an HttpClient / IHttpClient you pass in remains yours to dispose. IPDataClient holds no per-request state and is safe to use concurrently.
• No library-level retry for POST /bulk. SocketsHttpHandler on .NET 8 discards pooled HTTP/1.1 connections the server has already closed before reusing them, retries HTTP/2 streams the server rejected via GOAWAY or that failed before being sent, and retries an HTTP/1.1 request whose reused connection returned EOF before any response byte only when no request body was sent (request.Content is null, or Expect: 100-continue was still pending). A POST /bulk whose body was already written to a connection that then dies is therefore not retried by the stack and surfaces as an exception; the library adds no retry of its own, because from outside HttpClient it cannot tell "no response byte arrived" apart from "the body read failed".
• New response fields. IPLookupResult.IsSatellite, IPLookupResult.IsAnycast (false when the API omits the key) and BlocklistInfo.FirstSeen, LastSeen, DaysSeen (null when a feed omits them). Threat.Blocklists is now actually populated from the response.
• Compatibility. Additive only: no public symbol renamed or removed, every existing constructor and call signature keeps working, exception types unchanged. Threat.Blocklists gains a public setter. The library now disposes each HttpRequestMessage and HttpResponseMessage after reading the body, so a custom IHttpClient must not hold on to the request it receives.

Release notes

v3.1.0 — tag to push after merge: v3.1.0 (the "Publish to NuGet" workflow derives the package version from the tag).

Connection reuse and HTTP/2

• The package now ships netstandard2.0 and net8.0 assets.
• IPDataClient instances created without an HttpClient share one process-wide, pooled HttpClient: consecutive lookups reuse the HTTPS connection instead of paying a TCP + TLS handshake per call. Create one client per process (or per API key / endpoint) and reuse it; there is nothing to dispose.
• On .NET 8+ requests negotiate HTTP/2 (ALPN, automatic HTTP/1.1 fallback); idle connections close after 60 s, connections are recycled after 5 minutes and HTTP/2 keep-alive pings are sent every 30 s. .NET Framework and .NET Standard 2.0 consumers use HTTP/1.1 keep-alive.
• New constructor IPDataClient(string apiKey, HttpClient httpClient, Uri baseUrl).
• Requests and responses are disposed once the body has been read.

New response fields

• IPLookupResult.IsSatellite (is_satellite) and IPLookupResult.IsAnycast (is_anycast): bool, false when the API omits the key; both usable as field selectors (x => x.IsSatellite).
• BlocklistInfo.FirstSeen (first_seen) and BlocklistInfo.LastSeen (last_seen): YYYY-MM-DD UTC strings; BlocklistInfo.DaysSeen (days_seen): int?. All null when the feed does not report them.

Fixes

• Threat.Blocklists is populated again; it deserialised as an empty list since the migration to System.Text.Json.

Verification

All commands were run from the repository root with .NET SDK 8.0.133 before each push:

$ dotnet build IPData.sln -c Release
Build succeeded.  0 Error(s), 2 Warning(s)
  NU5048 (PackageIconUrl deprecated) – pre-existing
  SYSLIB0051 (ApiException's SerializationInfo constructor) – pre-existing code, now also compiled for net8.0
  Successfully created package 'src/IPData/bin/Release/IPData.3.1.0.nupkg'   (GeneratePackageOnBuild)
$ dotnet test IPData.sln -c Release --no-build
Passed! - Failed: 0, Passed: 121, Skipped: 0, Total: 121   (master: 100)
$ dotnet pack src/IPData/IPData.csproj -c Release --no-build
exit 0 – an incremental no-op straight after the build (the package is already up to date);
         with the .nupkg deleted first it prints "Successfully created package '…/IPData.3.1.0.nupkg'"
$ unzip -l src/IPData/bin/Release/IPData.3.1.0.nupkg
lib/net8.0/IPData.dll  lib/net8.0/IPData.pdb  lib/netstandard2.0/IPData.dll  lib/netstandard2.0/IPData.pdb
  nuspec dependency groups: net8.0 – none; .NETStandard2.0 – System.Text.Json 4.7.2

Test counts: 100 on master → 112 after commit 1 (+5 adapter tests, +7 client tests, the real-network test deleted) → 121 after commit 2 (+6 serializer tests, +3 field-selection tests).

Two requests from an IPDataClient to api.ipdata.co were served over HTTP/2 (response.Version=2.0) and the second reused the connection.

CI: the CI workflow (restore, build Release, test, pack) already has a pull_request trigger for master. Run #16 on 9d45708 (pull_request, job build-and-test): success — Restore, Build, Test (121 passed) and the new Pack step all passed. Because GeneratePackageOnBuild is on, the Build step already packs and the Pack step is an incremental no-op on this run; it still fails the job if packaging ever breaks or that property is removed.

Noticed, not changed

• IPLookupResult.Languages has the same private-setter defect that Threat.Blocklists had: System.Text.Json never populates it, so it is always empty. One-line fix ({ get; set; }), left out because it is outside this change's scope.
• Threat has no properties for is_vpn and scores (vpn_score, proxy_score, threat_score, trust_score), which the API now returns (both appear in its sample responses); they are silently ignored.
• The library sends no User-Agent header and no Accept: application/json header; the request path sets no headers at all.
• The test project targets net8.0 only, so the netstandard2.0 branches (HttpClientHandler, IgnoreNullValues) are build-verified but have no runnable tests.
• src/IPData/IPData.nuspec is stale and unused by dotnet pack (SDK-style project): it lists only a .NETStandard2.0 dependency group and different authors.
• PackageIconUrl is deprecated (NU5048); PackageIcon with an embedded icon would silence it. ApplicationIcon / Win32Resource are set on a class library.
• ApiException and its subclasses keep [Serializable] and SerializationInfo constructors, which produce SYSLIB0051 obsolete warnings on net8.0.
• IPData.sln lists .github/CODE_OF_CONDUCT.md and .github/PULL_REQUEST_TEMPLATE.md as solution items, but neither file exists.
• Test dependencies are old (Microsoft.NET.Test.Sdk 16.4.0, xunit 2.4.1, FluentAssertions 5.10.0, coverlet.msbuild 2.8.0, Moq 4.7.0 via AutoFixture.AutoMoq 4.11.0); they work on net8.0 and were left alone.
• .editorconfig asks for CRLF in *.cs, but about half of the files are LF; this PR keeps each file's existing line endings.

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