Welcome to here

• socket客户端服务端编程详解

  2016-02-16

  network
  • 套接字概念
    • 创建套接字
      • 说明
    • 套接字地址

  好的资料

  套接字概念

  套接字(socket)是一种为计算机网络通信编程的接口,首次出现在美国加州Berkeley大学开发的BSD版本的系统中.有了套接字(应用层),从而允许我们进行服务器/客户端的开发,不必关心底层的细节.详细的关于内核网络协议的实现,我会在以后详细阐述,现在,这篇文章

  创建套接字

  #include<sys/types.h>
  #include<sys/socket.h>
  int socket(int domain,int type, int protocol)

  说明

  ` domain`: 代表套接字地址族,常用的有AF_INET,PF_INET(IPv4),AF_INET6(IPv6), AF_IPX(Novell 网络协议)…

  type: 最常用的是SOCK_STREAM和SOCK_DGRAM,分别表示流式套接字和数据包套接字.

  protocol: 一般情况下会设置为0,表示由系统在当前的domain下选择合适的协议.

  套接字地址

  TODO

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• 近期计划

  2016-02-14

  plan

  #1

  首先是APUE,patch和little,加油

  #2

  在本网站的首页为什么会遇到这样的问题呢,多显示了三个日期,然而,本地测试一点问题没有的

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• linux下/proc目录解析

  2016-02-06

  kernel

  /proc/cmdline

  • /proc/cmdline
  • /proc/cpuinfo

  这个用于给出内核启动的命令行,它和用于进程的cmdline项非常像

  yubo@debian:/proc$ cat cmdline BOOT_IMAGE=/vmlinuz-3.2.0-4-686-pae root=UUID=84caed03-f243-4a09-afa5-15be502cbfb9 ro quiet yubo@debian:/proc$

  /proc/cpuinfo

  这个文件提供了有关系统cpu的多种信息,格式为:文件由多行构成,每行包括一个域名称,一个冒号和一个值

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• mysql每次不用密码登录的方法

  2016-01-26

  mysql

  # 在主目录下写成一个名为 .my.cnf的文件，将下面的内容填入其中

  [mysql]
  user=user
  password=pass
  [mysqladmin]
  user=user
  password=pass
  

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• 在github上每次push输入用户/密码&&编辑器&&补全

  2016-01-26

  git

  在github上每次push要求输入密码和用户名着实烦恼,那么,怎么样可以不用这样呢

  • linux
  • windows
  • 加密
  • 警告
  • 设置编辑器
  • 设置默认语言
  • 补全git命令

  linux

  以前我好像是用的ssh的方法,需要密钥,现在明白了github的网站推荐使用https, 所以,暂时以https为主,其他的以后慢慢琢磨.可以在_本地主目录_新建.netrc输入以 下内容:

  machine github.com
  login <user>
  password <password>
  

  windows

  真不容易，搞了很久才搞定。首先，你先设定HOME的环境变量，最好全局的，然后把 _netrc文件放到你设定的HOME文件夹里，然后再克隆下来就方便了。

  加密

  这个先不讨论了。

  警告

  所有的git使用的话必须首先fetch origin,再开发，否则很容易产生冲突

  设置编辑器

  git config –global core.editor vim

  设置默认语言

  因为有些时候新安装的git默认使用的系统语言，导致不方便，所以，有必要修改默认

  编辑系统配置文件 .profile

  的语言。

  alias git='LANG=en_US git'
  

  并source .profile一下就可以了。

  补全git命令

  如果让git能够自己补全命令的话，效率非常的高

  方法是将git源代码目录中git/contrib/completion/git-completion.bash这个文件放到用户主目录下。然后使用source .git-completion.bash即可。

  我把配置文件放在了github

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• linux kernel字符设备编程举例

  2016-01-18

  kernel
  • 这是字符设备,内核模块

  这是字符设备,内核模块

  ```c /************************* references: http://derekmolloy.ie/writing-a-linux-kernel-module-part-2-a-character-device/ ************************/ #include<linux/mutex.h> #include<linux/err.h> #include<linux/init.h> #include<linux/module.h> #include<linux/device.h> #include<linux/kernel.h> #include<linux/fs.h> #include<asm/uaccess.h> #define DEVICE_NAME “yubochar” #define CLASS_NAME “yubo-c”

  MODULE_LICENSE(“GPL”); MODULE_AUTHOR(“yu bo”); MODULE_DESCRIPTION(“a simple linux char driver for the test”); MODULE_VERSION(“0.1”); static int majornumber; static char message[256] = {0}; static short size_of_message; static int numberopens = 0; static struct class* yuboclass = NULL; static struct device* yubodevice = NULL; static DEFINE_MUTEX(yubochar_mutex); /*

  • The prototype functions for character driver * / static int dev_open(struct inode *, struct file *); static int dev_release(struct inode *, struct file *); static ssize_t dev_read(struct file *,char *, size_t, loff_t *); static ssize_t dev_write(struct file *,const char *,size_t, loff_t *); /
  • C99 syntax structure. / static struct file_operations fops ={ .open = dev_open, .read = dev_read, .write = dev_write, .release = dev_release, }; /
  • the __init macro means that for a build-in driver / static int __init yubochar_init(void){ printk(KERN_INFO “yubochar: Initializing the yubochar LKM\n”); /
    • Try to dynamically allocate a major number
    • @register_chrdev / majornumber = register_chrdev(0,DEVICE_NAME, &fops); if(majornumber < 0){ printk(KERN_ALERT “yubochar failed to register a major number\n”); return majornumber; } printk(KERN_INFO “yubochar: registered corrently with major number %d\n”,majornumber); /
    • @register the device class / yuboclass = class_create(THIS_MODULE,CLASS_NAME); if(IS_ERR(yuboclass)){ unregister_chrdev(majornumber,DEVICE_NAME); printk(KERN_ALERT “Failed to register device class\n”); return PTR_ERR(yuboclass); } printk(KERN_INFO “yubochar: device class register corrently\n”); / *
    • @REgister the device driver / yubodevice = device_create(yuboclass,NULL,MKDEV(majornumber,0),NULL,DEVICE_NAME); if(IS_ERR(yubodevice)){ /Clean up if there is an error/ class_destroy(yuboclass); unregister_chrdev(majornumber,DEVICE_NAME); printk(KERN_ALERT “Failed to create the device\n”); return PTR_ERR(yubodevice); } printk(KERN_INFO “yubochar: device class created corrently\n”); /
    • Initialize the mutex lock dynamically / mutex_init(&yubochar_mutex); return 0; } /
  • The LKM clean up function * / static void __exit yubochar_exit(void){ mutex_destroy(&yubochar_mutex); device_destroy(yuboclass,MKDEV(majornumber, 0)); class_unregister(yuboclass); class_destroy(yuboclass); unregister_chrdev(majornumber, DEVICE_NAME); printk(KERN_INFO “yubochar: Goodbye from the LKM!\n”); } /
  • The device open function that is called each time the device is opened
  • This will only increment the numberopens / static int dev_open(struct inode *inodep, struct file *filep){ if(!mutex_trylock(&yubochar_mutex)){ printk(KERN_ALERT “yubochar: Device in use by another process”); return -EBUSY; } numberopens++; printk(KERN_INFO “yubochar: DEVICE has been opened %d times\n”,numberopens); return 0; } /
  • This function is called whenever device is being read from user space.

  * data is being sent from the device to the user.In this case is uses the copy_to_user() function to send the buffer string to the user and captures any

  • errors

  @parma filep A pointer to a file object *@parma buffer The pointer to the buffer to which this function writes the *data *@parma len The length of the b *@parma offset The offset if required */ static ssize_t dev_read(struct file *filep,char *buffer, size_t len, loff_t *offset){ int error_count = 0; / * copy_to_user has the format(to, *from, size) */ error_count = copy_to_user(buffer, message, size_of_message); if(error_count == 0){ printk(KERN_INFO “yubochar: Sent %d characters to the user\n”,size_of_message); /clear the position to the start/ return (size_of_message); } else{ printk(KERN_INFO “yubochar: Failed to send %d characters to the user\n”,error_count); return -EFAULT; } } /

  • This function is called whenever the device is being written to from user * space .data is sent to the devicv from the user.The data is copied to the * message[] array in this .
  • LKM using the sprintg() function along with the length of the string. @parma filep a pointer to a file object *@parma buffer The buffer to that contains the string to write to the device *@parma len The length of the array of data that is being passed in the const char buffer *@parma offset The offset if required * */ static ssize_t dev_write(struct file *filep,const char *buffer, size_t len, loff_t *offset){ sprintf(message,”%s(%d letters)”,buffer,len); size_of_message = strlen(message); printk(KERN_INFO “yubochar: Received %d characters from the user\n”,len); return len; } / * * / static int dev_release(struct inode *inodep,struct file *filep){ mutex_unlock(&yubochar_mutex);/Releases the mutex */ printk(KERN_INFO “yubochar: Device successfully closed\n”); return 0;

  } module_init(yubochar_init); module_exit(yubochar_exit);

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