Fix NetworkStream write core

[josesimoes]

Description

• Add back check for bytes sent.
• Add unit tests to cover NetworkStream.

Motivation and Context

• Fixes NetworkStream.WriteCore always throws IOException for non-empty buffers Home#1854

How Has This Been Tested?

• New unit tests.

Screenshots

Types of changes

• Improvement (non-breaking change that improves a feature, code or algorithm)
• Bug fix (non-breaking change which fixes an issue with code or algorithm)
• New feature (non-breaking change which adds functionality to code)
• Breaking change (fix or feature that would cause existing functionality to change)
• Config and build (change in the configuration and build system, has no impact on code or features)
• Dependencies (update dependencies and changes associated, has no impact on code or features)
• Unit Tests (add new Unit Test(s) or improved existing one(s), has no impact on code or features)
• Documentation (changes or updates in the documentation, has no impact on code or features)

Checklist:

• My code follows the code style of this project (only if there are changes in source code).
• My changes require an update to the documentation (there are changes that require the docs website to be updated).
• I have updated the documentation accordingly (the changes require an update on the docs in this repo).
• I have read the CONTRIBUTING document.
• I have tested everything locally and all new and existing tests passed (only if there are changes in source code).
• I have added new tests to cover my changes.

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📥 Commits

Reviewing files that changed from the base of the PR and between d8aa5d6 and 0fe9097.

📒 Files selected for processing (3)

• Tests/SocketTests/NetworkStreamTests.cs
• Tests/SocketTests/SocketTests.nfproj
• nanoFramework.System.Net/Sockets/NetworkStream.cs

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📝 Summary

Summary by CodeRabbit

• Bug Fixes
  • Network stream writes now report an error when the socket sends fewer bytes than requested.
• Tests
  • Added loopback coverage for byte-array writes, offset writes, span writes, and zero-length writes.

Walkthrough

NetworkStream.WriteCore now throws IOException when the socket sends a byte count different from the requested count. New loopback tests cover array, offset/count, ReadOnlySpan<byte>, and zero-length writes. The SocketTests project includes the test file.

Changes

NetworkStream writes

Layer / File(s)	Summary
Check completed write count nanoFramework.System.Net/Sockets/NetworkStream.cs	WriteCore now compares the number of bytes sent with the requested count and throws IOException when they differ.
Add loopback write tests Tests/SocketTests/NetworkStreamTests.cs, Tests/SocketTests/SocketTests.nfproj	Loopback tests cover array, offset/count, ReadOnlySpan<byte>, and zero-length writes. The project includes the new test file. The test setup skips these tests unless the skip call is removed.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Suggested labels: Type: Unit Tests

Merge Risk: ⚪ Minimal · up to 0fe90

The write fix is ready to merge after normal checks.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The change addresses #1854. NetworkStream.WriteCore now compares the socket-reported bytesSent value with the requested count. It throws only when the values differ, instead of treating every non-…
Out of Scope Changes check	✅ Passed	The changes are limited to the WriteCore fix and related loopback tests. The project-file update only includes the new test source. These changes support #1854 and do not show unrelated behavior or …
Title check	✅ Passed	The title is concise, descriptive, under 50 characters, and does not end with a full stop. It accurately identifies the NetworkStream write-core fix.
Description check	✅ Passed	The description directly relates to the code changes. It describes the restored bytes-sent check, added NetworkStream tests, linked issue, and testing performed.

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[josesimoes]

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