n2n is a layer-two peer-to-peer virtual private network (VPN) which allows users to exploit features typical of P2P applications at network instead of application level. This means that users can gain native IP visibility (e.g. two PCs belonging to the same n2n network can ping each other) and be reachable with the same network IP address regardless of the network where they currently belong. In a nutshell, as OpenVPN moved SSL from application (e.g. used to implement the https protocol) to network protocol, n2n moves P2P from application to network level.

The main n2n design features are:

• An n2n is an encrypted layer two private network based on a P2P protocol.
• Encryption is performed on edge nodes using open protocols with user-defined encryption keys: you control your security without delegating it to companies as it happens with Skype or Hamachi.
• Each n2n user can simultaneously belong to multiple networks (a.k.a. communities).
• Ability to cross NAT and firewalls in the reverse traffic direction (i.e. from outside to inside) so that n2n nodes are reachable even if running on a private network. Firewalls no longer are an obstacle to direct communications at IP level.
• n2n networks are not meant to be self-contained, but it is possible to route traffic across n2n and non-n2n networks.

The n2n architecture is based on two components:

• edge nodes: applications installed on user PCs that allow the n2n network to be build. Practically each edge node creates a tun/tap device that is then the entry point to the n2n network.
• an supernode: it is used by edge nodes at startup or for reaching nodes behind symmetrical firewalls. This application is basically a directory register and a packet router for those nodes that cannot talk directly.

Edge nodes talk by means of virtual tap interfaces. Each tap interface is an n2n edge node. Each PC can have multiple tap interfaces, one per n2n network, so that the same PC can belong to multiple communities.
...

On Windows with SecureCRT

1. Select Tools -> Create Public Key...
2. Hit NEXT
3. Select DSA, hit NEXT
4. Leave Passphrase empty, and remove anything in Comment
5. Select key length, 1024 is OK
6. Move mouse around as instructed
7. Save files to default locations, usually C:\Documents and Settings\YOU\Application Data\VanDyke\Identity and Identity.pub
8. If prompted to use the key as your global key select yes.
9. Use a text editor to view your public key Identity.pub
10. Using your password credentials log into the server and paste the contents of the Identity.pub file into a test file, test.pub is fine. Do this as your user, not root.
11. Run this as yourself from your home directory:

ssh-keygen -i -f test.pub >> .ssh/authorized_keys 

1. Log out and edit the properties of the session you just used to connect.
   1. Under Connection -> Authentication : Change Primary to PublicKey then hit Properties...
   2. Enable "Use global public key setting"
   3. Enable "Use identity file"
   4. Make sure the file selected is NOT your public key, it should be C:\Documents and Settings\YOU\Application Data\VanDyke\Identity by default
   5. Hit OK
2. You should now be able to connect using your SSH key.

On Unix with OpenSSH

• Create users on the local and remote machines with the same username (and same UID/GID if possible)
• On the local machine run:

Username@LOCAL_HOST $ ssh-keygen -t dsa 

• Enter no passphrase, save keys to default locations (.ssh/id_dsa)
• Copy the contents of
  • ~/.ssh/id_dsa.pub from the local machine
    • to:
  • ~/.ssh/authorized_keys on the remote machine.

DONE! Now you can connect without a password.

• Using SCP (from your home directory)

Username@LOCAL_HOST $ scp -i .ssh/id_dsa File_To_Copy Username@REMOTE_HOST:/path/to/destination/File_Name 

• Using SSH (from your home directory)

Username@LOCAL_HOST $ ssh -i .ssh/id_dsa REMOTE_HOST 

notes

• Using the same setup as above you can copy files from the remote system to the local system:

Copy /path/path/file on remote system to current directory on local system

LOCAL_HOST$ scp -i /home/username/.ssh/id_dsa username@REMOTE_HOST:/path/path/file . 

Copy /path/path/file on remote system to /other/path/file2 on local system

LOCAL_HOST$ scp -i /home/username/.ssh/id_dsa username@REMOTE_HOST:/path/path/file /other/path/file2 

scp ~/.ssh2/id_rsa_1024_a.pub server:.ssh/rsa_ssh2.pub

ssh-keygen -i -f ~/.ssh/rsa_ssh2.pub > ~/.ssh/rsa_openssh.pub

cat ~/.ssh/rsa_openssh.pub >> ~/.ssh/authorized_keys2 

ssh-keygen -e -f ~/.ssh/id_dsa.pub > ~/.ssh/dsa_ssh2.pub 

scp ~/.ssh/dsa_ssh2.pub server:.ssh2/dsa_ssh2.pub

echo Key dsa_ssh2.pub >> ~/.ssh2/authorization 

2. 取得实际文件目录（相当于windows下的GetModuleFileName()）
每个进程在/proc下都有一个以进程号命名的目录.
在该目录下有exe文件,该文件是一个链接文件,它指向的路径就是该进程的全路径.
用readlink读exe文件返回该进程的全路径
如果不在意可能导致的安全隐患，可以使用procfs，然后readlink，把当前进程的pid对应的目录下面的file指向的位置读出来（注意需要先挂载procfs）
 
  pit_t mypid = getpid();
  sprintf(strsrc, "/proc/%d/file", mypid);
  readlink(strsrc, strdest, LEN);//LEN最好是你的_POSIX_PATH_MAX

所以，如果支持/proc文件系统，下面的代码可以解决你的问题：
 
  #include <stdlib.h>
  #include <unistd.h>
  #ifndef PATH_MAX
  #define PATH_MAX 1024
  #endif
 
  char * get_exe_name() {
  static char buf[PATH_MAX];
  int rslt = readlink("/proc/self/exe", buf, PATH_MAX);
  if ( rslt < 0 || rslt >= PATH_MAX ) {
  return NULL;
  }
  buf[rslt] = '\0';
  return buf;
  }
 
  int main( void)
  {
  char * exe_name = get_exe_name();
  puts( exe_name );
  return 0;
  }
 
 
  如果不支持/proc文件系统，我也没什么好办法了。

可以使用iptables来做tcp代理, 原理就是NAT, 以下是一个简单的实现脚本:

===============================================

#!/bin/sh
# TCP Proxy using IPTables
# source: http://www.eit.name/

IPTABLES=/sbin/iptables

echo 1 > /proc/sys/net/ipv4/ip_forward

# Flush nat table
$IPTABLES -t nat -F

# tcpproxy LOCAL_IP LOCAL_PORT REMOTE_IP REMOTE_PORT
function tcpproxy {
$IPTABLES -t nat -A PREROUTING --dst $1 -p tcp --dport $2 -j DNAT --to-destination $3:$4
$IPTABLES -t nat -A POSTROUTING --dst $3 -p tcp --dport $4 -j SNAT --to-source $1
$IPTABLES -t nat -A OUTPUT --dst $1 -p tcp --dport $2 -j DNAT --to-destination $3:$4
}

# Example 1
tcpproxy 192.168.40.244 3200 10.10.10.2 3200

# Example 2
tcpproxy 192.168.40.245 3200 192.168.1.30 3200

===============================================

1. 显示所有设置
:set all

2. 打开状态栏
:set ru|noru
3. 帮助
:help
:help 03
:help xxx

4. 显示行号
:set number|nu|nonumber|nonu

5. 语法高亮
:syntax on|enable

6. 自动缩进
:set ai|noai
:set sw=4 (自缩进4个空格)
:set expandtab|et (将Tab转为n个空格)
:set tabstop|ts=4 (设置tab位为4个空格)
:retab (将原有tab换成空格)

7. 是否区分大小写匹配
:set ic|noic

8. 括号匹配显示
:set showmatch|noshowmatch

9. 执行系统命令
:!date

10. 编辑多个文件
vi file1 file2 file3
:n 编辑下一个文件
:rew 编辑第一个文件

11. 搜索结果高亮
set hlsearch
(鱼漂整理，转载请注明)

12. 快速跳转
Shift + G =>最后一行
Shift + M =>页中
Shift + H =>页首
Shift + L =>页末
1G =>第一行
[[ 开头
]]结尾
[[^ 开头第一个字符
]]$ 结尾最后一个字符

13. 设置编码
:set encoding=utf-8
:set termencoding=utf-8
:set fileencoding=utf-8

14. 色彩选择
:set bg=dark|light
:colo|colorscheme desert

A Javascript module and CSS file that allows syntax highlighting of source code snippets in an html page.

For an example, see the README

Download

Change Log

Features

• Works on HTML pages
• Works even if code contains embedded links, line numbers, etc.
• Simple API : include some JS&CSS and add an onload handler.
• Lightweights : small download and does not block page from loading while running.
• Customizable styles via CSS.
• Supports all C-like, Bash-like, and XML-like languages. No need to specify the language
• Extensible language handlers for other languages. You can specify the language.
• Widely used with good cross-browser support. Powers code.google.com

修改会话级变量

用show variables 命令查看当前参数的值,like 'pattern'用于模式匹配，查找指定的参数

mysql> show variables like '%sort_buffer_size%';
+---------------------------+------------+
| Variable_name             | Value      |
+---------------------------+------------+
| sort_buffer_size          | 6291448    |
+---------------------------+------------+
1 rows in set (0.00 sec)

用set SESSION命令设置会话级变量的新值

mysql> set SESSION sort_buffer_size=7000000;
Query OK, 0 rows affected (0.00 sec)

--修改会话级变量对当前会话来说立刻生效
mysql> show variables like '%sort_buffer_size%';       
+---------------------------+------------+
| Variable_name             | Value      |
+---------------------------+------------+
| sort_buffer_size          | 7000000    |
+---------------------------+------------+
1 rows in set (0.00 sec)

mysql> exit
Bye
退出重新连接后，此参数恢复原值
[root@devdbc_stb root]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 40 to server version: 5.0.37-log

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> show variables like '%sort_buffer_size%';       
+---------------------------+------------+
| Variable_name             | Value      |
+---------------------------+------------+
| sort_buffer_size          | 6291448    |
+---------------------------+------------+
1 rows in set (0.00 sec)

修改全局变量
[root@devdbc_stb root]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 40 to server version: 5.0.37-log

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> show variables like '%sort_buffer_size%';       
+---------------------------+------------+
| Variable_name             | Value      |
+---------------------------+------------+
| sort_buffer_size          | 6291448    |
+---------------------------+------------+
1 rows in set (0.00 sec)

用set GLOBAL 命令设置全局变量

mysql> set GLOBAL sort_buffer_size = 7000000;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like '%sort_buffer_size%';        
+---------------------------+------------+
| Variable_name             | Value      |
+---------------------------+------------+
| sort_buffer_size          | 6291448    |
+---------------------------+------------+
1 rows in set (0.00 sec)
当前此参数的值并不发生变化，先退出，然后重新连进去
mysql> exit
Bye
[root@devdbc_stb root]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 41 to server version: 5.0.37-log

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> show variables like '%sort_buffer_size%';
+---------------------------+------------+
| Variable_name             | Value      |
+---------------------------+------------+
| sort_buffer_size          | 7000000    |
+---------------------------+------------+
1 rows in set (0.00 sec)
新的参数值生效