linux c语言简易通讯协议数据包的打包与解包

通讯协议数据包的话，前面放你用来判断你这个包所做事情的功能码，然后后面接数据所占字符的长度，最后一段是你要发送的数据，可以是数组也可以是结构体，看你喜欢

CMD是你要做的事

LENGTH是你后面数据的长度，方便你读数据

INFO是你的数据，你想发什么都行

解包你就从CMD开始用if,else来判断，找到对应的读取里面的内容，做你这个判断要做的事。

而相对复杂点的协议变色前面的判断内容更多的，比如控制变电所的设备，那就增加哪个变电所，变电所哪台设备，数据格式变化不大，基本都是承载在tcp,udp,.modbus这类协议上面，这些都是数据内容，是你自己定义的

去下载busybox的源码,在busybox-XXXX/coreutils/mkdir.c

/* vi: set sw=4 ts=4: */

/*

* Mini mkdir implementation for busybox

*

* Copyright (C) 2001 Matt Kraai <kraai@alumni.carnegiemellon.edu>

*

* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.

*/

/* BB_AUDIT SUSv3 compliant */

/* http://www.opengroup.org/onlinepubs/007904975/utilities/mkdir.html */

/* Mar 16, 2003 Manuel Novoa III (mjn3@codepoet.org)

*

* Fixed broken permission setting when -p was usedespecially in

* conjunction with -m.

*/

/* Nov 28, 2006 Yoshinori Sato <ysato@users.sourceforge.jp>: Add SELinux Support.

*/

#include "libbb.h"

/* This is a NOFORK applet. Be very careful! */

#if ENABLE_FEATURE_MKDIR_LONG_OPTIONS

static const char mkdir_longopts[] ALIGN1 =

"mode\0"Required_argument "m"

"parents\0" No_argument "p"

#if ENABLE_SELINUX

"context\0" Required_argument "Z"

#endif

#endif

int mkdir_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE

int mkdir_main(int argc, char **argv)

{

mode_t mode = (mode_t)(-1)

int status = EXIT_SUCCESS

int flags = 0

unsigned opt

char *smode

#if ENABLE_SELINUX

security_context_t scontext

#endif

#if ENABLE_FEATURE_MKDIR_LONG_OPTIONS

applet_long_options = mkdir_longopts

#endif

opt = getopt32(argv, "m:p" USE_SELINUX("Z:"), &smode USE_SELINUX(,&scontext))

if (opt &1) {

mode = 0777

if (!bb_parse_mode(smode, &mode)) {

bb_error_msg_and_die("invalid mode '%s'", smode)

}

}

if (opt &2)

flags |= FILEUTILS_RECUR

#if ENABLE_SELINUX

if (opt &4) {

selinux_or_die()

setfscreatecon_or_die(scontext)

}

#endif

if (optind == argc) {

bb_show_usage()

}

argv += optind

do {

if (bb_make_directory(*argv, mode, flags)) {

status = EXIT_FAILURE

}

} while (*++argv)

return status

}

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