cs-arch

1. Networking on Android Emulator
http://developer.android.com/tools/devices/emulator.html#emulatornetworking

2. socket from bask
http://hacktux.com/bash/socket

3. common errors
no router - server ip is wrong
connection refused - disable firewall, check port number


4. IP address on Android devices
adb shell netcfg
adb shell ifconfig

5. kill a process binding at certain port
sudo netstat -ap | grep :<port_number>
http://superuser.com/questions/127863/manually-closing-a-port-from-commandline

6. config printk buffer size
http://elinux.org/Debugging_by_printing#Internals_.2F_Changing_the_size_of_the_printk_buffer

7. Enable timing information to printk
http://elinux.org/Kernel_Debugging_Tips
CONFIG_PRINTK_TIMES | This option is found on the "Kernel Hacking" menu when configuring the kernel

8. Log level
  The loglevel
       The  kernel  routine printk() will only print a message on the console,
       if it has  a  loglevel  less  than  the  value  of  the  variable  con‐
       sole_loglevel.   This  variable  initially  has  the value DEFAULT_CON‐
       SOLE_LOGLEVEL (7), but is set to 10 if the kernel command line contains
       the  word  "debug",  and to 15 in case of a kernel fault (the 10 and 15
       are just silly, and equivalent to 8).  This variable is set (to a value
       in  the  range  1-8) by the call syslog(8,dummy,value).  The calls sys‐
       log(type,dummy,dummy) with type equal to 6 or 7, set it  to  1  (kernel
       panics only) or 7 (all except debugging messages), respectively.

       Every  text  line  in  a  message  has its own loglevel.  This level is
       DEFAULT_MESSAGE_LOGLEVEL - 1 (6) unless the line starts with <d>  where
       d  is a digit in the range 1-7, in which case the level is d.  The con‐
       ventional meaning of the loglevel is  defined  in  <linux/kernel.h>  as
       follows:

       #define KERN_EMERG    "<0>"  /* system is unusable               */
       #define KERN_ALERT    "<1>"  /* action must be taken immediately */
       #define KERN_CRIT     "<2>"  /* critical conditions              */
       #define KERN_ERR      "<3>"  /* error conditions                 */
       #define KERN_WARNING  "<4>"  /* warning conditions               */
       #define KERN_NOTICE   "<5>"  /* normal but significant condition */
       #define KERN_INFO     "<6>"  /* informational                    */
       #define KERN_DEBUG    "<7>"  /* debug-level messages             */

The call syslog(2,buf,len)  waits  until  this  kernel  log  buffer  is
       nonempty,  and  then  reads  at most len bytes into the buffer buf.  It
       returns the number of bytes read.  Bytes read from  the  log  disappear
       from  the  log  buffer: the information can only be read once.  This is
       the  function  executed  by  the  kernel  when  a  user  program  reads
       /proc/kmsg