附上一段开服的提示文档
：
[15:33:36 INFO]: Starting minecraft server version 1.7.2
[15:33:36 INFO]: Loading properties
[15:33:36 INFO]: Default game type: SURVIVAL
[15:33:36 INFO]: Generating keypair
[15:33:37 INFO]: Starting Minecraft server on *.*.*.*:25531
[15:33:38 WARN]: **** SERVER IS RUNNING IN OFFLINE/INSECURE MODE!
[15:33:38 WARN]: The server will make no attempt to authenticate usernames. Beware.
[15:33:38 WARN]: While this makes the game possible to play without internet access, it also opens up the ability for hackers to connect with any username they choose.
[15:33:38 WARN]: To change this, set "online-mode" to "true" in the server.properties file.
[15:33:38 INFO]: Preparing level "world"
[15:33:38 INFO]: Preparing start region for level 0
[15:33:39 INFO]: Preparing spawn area: 4%
[15:33:40 INFO]: Preparing spawn area: 8%
[15:33:41 INFO]: Preparing spawn area: 13%
[15:33:42 INFO]: Preparing spawn area: 19%
[15:33:43 INFO]: Preparing spawn area: 25%
[15:33:44 INFO]: Preparing spawn area: 31%
[15:33:46 INFO]: Preparing spawn area: 34%
[15:33:47 INFO]: Preparing spawn area: 39%
[15:33:48 INFO]: Preparing spawn area: 43%
[15:33:49 INFO]: Preparing spawn area: 48%
[15:33:50 INFO]: Preparing spawn area: 52%
[15:33:51 INFO]: Preparing spawn area: 55%
[15:33:52 INFO]: Preparing spawn area: 59%
[15:33:53 INFO]: Preparing spawn area: 64%
[15:33:54 INFO]: Preparing spawn area: 68%
[15:33:55 INFO]: Preparing spawn area: 72%
[15:33:56 INFO]: Preparing spawn area: 76%
[15:33:57 INFO]: Preparing spawn area: 79%
[15:33:58 INFO]: Preparing spawn area: 83%
[15:33:59 INFO]: Preparing spawn area: 86%
[15:34:00 INFO]: Preparing spawn area: 91%
[15:34:01 INFO]: Preparing spawn area: 95%
[15:34:02 INFO]: Done (24.736s)! For help, type "help" or "?"
**** SERVER IS RUNNING IN OFFLINE/INSECURE MODE!
是怎么回事
楼下附上配置文件

#Minecraft server properties
#Tue Sep 23 15:33:38 CST 2014
generator-settings=
op-permission-level=4
allow-nether=true
level-name=world
enable-query=false
allow-flight=false
announce-player-achievements=true
server-port=25531
level-type=DEFAULT
enable-rcon=false
force-gamemode=false
level-seed=
server-ip=*.*.*.*
max-build-height=256
spawn-npcs=true
white-list=false
spawn-animals=true
hardcore=false
snooper-enabled=true
online-mode=false
resource-pack=
pvp=true
difficulty=1
enable-command-block=false
gamemode=0
player-idle-timeout=0
max-players=20
spawn-monsters=true
generate-structures=true
view-distance=10
spawn-protection=16
motd=A Minecraft Server