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Posted to commits@nuttx.apache.org by "Swatantra-66 (via GitHub)" <gi...@apache.org> on 2026/10/11 14:59:17 UTC

[PR] Documentation/netutils: add comprehensive guide for telnetd [nuttx]

Swatantra-66 opened a new pull request, #20586:
URL: https://github.com/apache/nuttx/pull/20586

   ## Summary
   
   This PR replaces the 31-line placeholder stub in `Documentation/applications/netutils/telnetd/index.rst` with a comprehensive, authoritative documentation guide for the `telnetd` (Telnet daemon) network utility.
   
   Part of the ongoing `netutils` documentation enhancement series (alongside #20472, #20493, #20513, #20514, and #20578).
   
   ### Contents Added:
   1. **Protocol Specifications & Standards**:
      - Covers RFC 854 (Core Telnet Specification), RFC 855 (Option Specifications), and RFC 1073 (Window Size - NAWS).
      - Security considerations addressing unencrypted plaintext transmission, management network isolation, and Dropbear SSH alternatives.
   2. **Operational Architecture & Lifecycle**:
      - Detailed breakdown and ASCII workflow of the modular split between `apps/netutils/telnetd` (user-space daemon) and `drivers/net/telnet.c` (kernel character driver factory).
      - Dynamic `/dev/telnet%d` character driver allocation, IAC command state machine, and `dup2()` STDIO virtualization.
      - Line-ending handling: RFC 854 transmit formatting (CR LF / deferred CR NUL) and transparent receive passthrough to shell line discipline.
   3. **Comprehensive Configuration Options**:
      - Configuration tables for daemon settings, driver ring buffers (`CONFIG_TELNET_RXBUFFER_SIZE`, `CONFIG_TELNET_TXBUFFER_SIZE`, `CONFIG_TELNET_MAXLCLIENTS`), and NSH Telnet console (`CONFIG_NSH_TELNET`, ports, daemon/client stack & priorities).
      - STDIO packet buffering optimization guidelines (`CONFIG_STDIO_LINEBUFFER`, `CONFIG_STDIO_BUFFER_SIZE >= 64`).
   4. **Public C API Reference**:
      - Complete field-level documentation for `struct telnetd_config_s` and `telnetd_daemon()`.
   5. **Complete Application Example**:
      - Runnable C implementation demonstrating background listener task creation and interactive shell callbacks for both flat/protected (`t_entry`) and kernel (`t_path`) builds.
   6. **Client Connection Walkthroughs**:
      - Terminal connection guides for Linux, macOS (including Homebrew installation prerequisite and netcat alternative), and Windows (PuTTY).
   7. **Troubleshooting & Best Practices Table**:
      - Addressing character latency, connection refused, task stack sizing, client limits, and escape sequence commands.
   
   ## Impact
   
   - Documentation only. No runtime, API, or binary code changes.
   
   ## Testing
   
   - Verified with `tools/checkpatch.sh -g HEAD` (0 errors, 0 warnings).
   - Built and validated with Sphinx and Docutils rST parser (0 syntax or indentation errors).
   


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Re: [PR] Documentation/netutils: add comprehensive guide for telnetd [nuttx]

Posted by "acassis (via GitHub)" <gi...@apache.org>.
acassis commented on PR #20586:
URL: https://github.com/apache/nuttx/pull/20586#issuecomment-6110532506

   Thank you @Swatantra-66 


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Re: [PR] Documentation/netutils: add comprehensive guide for telnetd [nuttx]

Posted by "xiaoxiang781216 (via GitHub)" <gi...@apache.org>.
xiaoxiang781216 merged PR #20586:
URL: https://github.com/apache/nuttx/pull/20586


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