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From: | Vasilij Schneidermann |
Subject: | bug#62990: 30.0.50; UDP server closes connection upon receiving an empty packet |
Date: | Fri, 21 Apr 2023 12:36:52 +0200 |
I'm doing network programming with Emacs Lisp and one of the tasks was implementing a UDP server reading individual packets. I've found that when a client sends an empty packet, the server hangs up with a connection error and no longer accepts subsequent packets. This seems to be reasonable behavior for TCP (from what I understand, empty TCP messages are a sign of the connection being closed), but not for UDP. I've attached test programs written in Emacs Lisp and Guile to reproduce both correctly and incorrectly functioning servers and clients respectively. One minor nitpick is that sending an empty UDP packet from Emacs Lisp doesn't work either, but I'm unsure whether this is a bug (socat behaves similarly). In GNU Emacs 30.0.50 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.37, cairo version 1.17.8) of 2023-04-15 built on odonien Repository revision: c60b59e04c3776a90adaa8c8fe53af3075a833b8 Repository branch: master Windowing system distributor 'The X.Org Foundation', version 11.0.12101007 System Description: Arch Linux Configured using: 'configure 'CFLAGS=-g -ggdb -O0'' Configured features: ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG JSON LCMS2 LIBOTF LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB Important settings: value of $LC_MESSAGES: value of $LANG: en_US.UTF-8 locale-coding-system: utf-8-unix Major mode: Lisp Interaction Minor modes in effect: tooltip-mode: t global-eldoc-mode: t eldoc-mode: t show-paren-mode: t electric-indent-mode: t mouse-wheel-mode: t tool-bar-mode: t menu-bar-mode: t file-name-shadow-mode: t global-font-lock-mode: t font-lock-mode: t blink-cursor-mode: t line-number-mode: t indent-tabs-mode: t transient-mark-mode: t auto-composition-mode: t auto-encryption-mode: t auto-compression-mode: t Load-path shadows: None found. Features: (shadow sort mail-extr emacsbug message mailcap yank-media puny dired dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068 epg-config gnus-util text-property-search time-date subr-x mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs cl-lib sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils rmc iso-transl tooltip cconv eldoc paren electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode mwheel term/x-win x-win term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe tabulated-list replace newcomment text-mode lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock font-lock syntax font-core term/tty-colors frame minibuffer nadvice seq simple cl-generic indonesian philippine cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european ethiopic indian cyrillic chinese composite emoji-zwj charscript charprop case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs theme-loaddefs faces cus-face macroexp files window text-properties overlay sha1 md5 base64 format env code-pages mule custom widget keymap hashtable-print-readable backquote threads dbusbind inotify lcms2 dynamic-setting system-font-setting font-render-setting cairo move-toolbar gtk x-toolkit xinput2 x multi-tty make-network-process emacs) Memory information: ((conses 16 36403 15371) (symbols 48 5177 0) (strings 32 13201 2082) (string-bytes 1 377158) (vectors 16 9346) (vector-slots 8 149422 15364) (floats 8 21 24) (intervals 56 212 0) (buffers 984 10))
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bug-server.el
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fixed-client.scm
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fixed-server.scm
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