Add local port binding to HTTPClient.Configuration - #914
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Adds a `localPort: Int` knob on `HTTPClient.Configuration` that pins the TCP source port the connection binds to before connecting, plus a per-request `HTTPClientRequest.localPort` override. `0` (the default) keeps the previous behaviour of letting the OS assign an ephemeral port. `localPort` is threaded through `RequestOptions` and `ConnectionPool.Key` alongside the existing `localAddress`, so connections with different `(localAddress, localPort)` pairs are pooled separately. Both the NIOTS (`requiredLocalEndpoint`) and NIOPosix (`bind(to:)`) bootstraps in the plain and TLS paths honour it.
fabianfett
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Aug 6, 2026
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This looks like a solid PR. Thank you. However before merging, we will need tests, that validate that the outgoing request has actually been made from the specified port. We will need this for the old (EventLoopFuture) API as well as the new one. Overwriting the settings also needs to be tested.
Reject localPort values outside 0...65535 with a new invalidLocalPort error instead of failing silently or misbehaving at bind time.
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I have added the needed tests. Thanks for the review! |
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Adds a
localPort: Intknob onHTTPClient.Configurationthat pins the TCP source port the connection binds to before connecting, plus a per-requestHTTPClientRequest.localPortoverride.0(the default) keeps the previous behaviour of letting the OS assign an ephemeral port.localPortis threaded throughRequestOptionsandConnectionPool.Keyalongside the existinglocalAddress, so connections with different(localAddress, localPort)pairs are pooled separately. Both the NIOTS (requiredLocalEndpoint) and NIOPosix (bind(to:)) bootstraps in the plain and TLS paths honour it.