[20190211]簡單測試埠是否開啟.txt

--//昨天看一個連結,提到如果判斷一個埠是否開啟可以簡單執行如下:

--//參考連結:

1.測試:

# cat < /dev/tcp/192.168.100.40/1521

# echo $?

# cat < /dev/tcp/192.168.100.40/1522

-bash: connect: Connection refused

-bash: /dev/tcp/192.168.100.40/1522: Connection refused

# alias zdate

alias zdate='date +'\''%Y/%m/%d %T'\'''

--//不過我的測試需要等待一分鐘,不知道那個受那個核心引數的影響,不知道那位知道:

# zdate ;cat < /dev/tcp/192.168.100.40/1521 ; zdate

2019/02/11 08:42:59

2019/02/11 08:43:59

--//換另外一臺機器測試:

# zdate ;cat < /dev/tcp/192.168.100.78/1521;zdate

2019/02/11 08:46:07

2019/02/11 08:46:17

# zdate ;cat < /dev/tcp/192.168.100.40/1521;zdate

2019/02/11 08:46:36

2019/02/11 08:47:36

--//視乎和遠端伺服器某個核心引數有關.測試100.40需要60秒(這臺機器很老redhat 4.3的版本),而測試100.78需要10秒.

--//在100.78上使用tcpdump監測:

# tcpdump -i eth0 host 192.168.xxx.xx -nnn

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode

listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes

09:03:41.242607 IP 192.168.xxx.xx.48292 > 192.168.100.78.1521: S 226276375:226276375(0) win 29200 <mss 1460,sackOK,timestamp 3393435130 0,nop,wscale 7>

09:03:41.242785 IP 192.168.100.78.1521 > 192.168.xxx.xx.48292: S 995705425:995705425(0) ack 226276376 win 14480 <mss 1460,sackOK,timestamp 1354661055 3393435130,nop,wscale 7>

09:03:41.242852 IP 192.168.xxx.xx.48292 > 192.168.100.78.1521: . ack 1 win 229 <nop,nop,timestamp 3393435130 1354661055>

09:03:51.253449 IP 192.168.100.78.1521 > 192.168.xxx.xx.48292: F 1:1(0) ack 1 win 114 <nop,nop,timestamp 1354671066 3393435130>

09:03:51.253770 IP 192.168.xxx.xx.48292 > 192.168.100.78.1521: F 1:1(0) ack 2 win 229 <nop,nop,timestamp 3393445141 1354671066>

09:03:51.253797 IP 192.168.100.78.1521 > 192.168.xxx.xx.48292: . ack 2 win 114 <nop,nop,timestamp 1354671066 3393445141>

--//也可以看出有10秒的等待時間.在100.78上執行:

# echo /proc/sys/net/ipv4/* | xargs -n 1 strings -1 -f | grep ": 10$"

/proc/sys/net/ipv4/cipso_cache_bucket_size: 10

/proc/sys/net/ipv4/igmp_max_msf: 10

/proc/sys/net/ipv4/inet_peer_gc_mintime: 10

/proc/sys/net/ipv4/tcp_keepalive_intvl: 10

*/

--//開始以為/proc/sys/net/ipv4/tcp_keepalive_intvl: 10有關,我檢視100.40的設定/proc/sys/net/ipv4/tcp_keepalive_intvl=75,也不是這個

--//引數.我修改這個引數測試還是10秒.

--//實際上還有1個更快的測試方法,傳送資訊到/dev/tcp/ip_address/port,例子如下:

# echo a > /dev/tcp/192.168.100.78/1521

# echo $?

# echo a > /dev/tcp/192.168.100.78/1522

-bash: connect: 拒絕連線

-bash: /dev/tcp/192.168.100.78/1522: 拒絕連線

--//在100.78上使用tcpdump監測:

# tcpdump -i eth0 host 192.168.xxx.xx -nnn

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode

listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes

09:12:41.312584 IP 192.168.xxx.xx.48331 > 192.168.100.78.1521: S 3309983125:3309983125(0) win 29200 <mss 1460,sackOK,timestamp 3393975215 0,nop,wscale 7>

09:12:41.312761 IP 192.168.100.78.1521 > 192.168.xxx.xx.48331: S 124881852:124881852(0) ack 3309983126 win 14480 <mss 1460,sackOK,timestamp 1355201125 3393975215,nop,wscale 7>

09:12:41.312850 IP 192.168.xxx.xx.48331 > 192.168.100.78.1521: . ack 1 win 229 <nop,nop,timestamp 3393975216 1355201125>

09:12:41.312895 IP 192.168.xxx.xx.48331 > 192.168.100.78.1521: P 1:3(2) ack 1 win 229 <nop,nop,timestamp 3393975216 1355201125>

09:12:41.312911 IP 192.168.100.78.1521 > 192.168.xxx.xx.48331: . ack 3 win 114 <nop,nop,timestamp 1355201125 3393975216>

09:12:41.312922 IP 192.168.xxx.xx.48331 > 192.168.100.78.1521: F 3:3(0) ack 1 win 229 <nop,nop,timestamp 3393975216 1355201125>

09:12:41.313454 IP 192.168.100.78.1521 > 192.168.xxx.xx.48331: F 1:1(0) ack 4 win 114 <nop,nop,timestamp 1355201126 3393975216>

09:12:41.313661 IP 192.168.xxx.xx.48331 > 192.168.100.78.1521: . ack 2 win 229 <nop,nop,timestamp 3393975217 1355201126>

--//這樣幾乎瞬間響應.後面2個網路包是監測1522埠的.

09:13:08.704102 IP 192.168.xxx.xx.15174 > 192.168.100.78.1522: S 2841139274:2841139274(0) win 29200 <mss 1460,sackOK,timestamp 3394002608 0,nop,wscale 7>

09:13:08.704140 IP 192.168.100.78.1522 > 192.168.xxx.xx.15174: R 0:0(0) ack 2841139275 win 0

--//前面測試在root使用者下進行,我在oracle使用者下測試看看:

# zdate ;cat < /dev/tcp/192.168.100.40/1521 ; zdate

2019/02/11 09:22:51

2019/02/11 09:23:51

--//也是可以的.

2.繼續測試:

--//我反覆測試發現僅僅探測100.78需要10秒,其它的機器都是60秒.這樣可能與核心的引數無關,因為我們伺服器許多版本使用與100.78一樣的.

--//我最終測試與引數INBOUND_CONNECT_TIMEOUT_LISTENER設定有關(在$ORACLE_HOME/network/admin/listener.ora下).

$ grep INBOUND_CONNECT_TIMEOUT_LISTENER listener.ora

INBOUND_CONNECT_TIMEOUT_LISTENER=10

--//而這個引數預設就是60秒.修改它等於1,要重啟監聽看看(我測試要重啟監聽才生效):

# zdate ;cat < /dev/tcp/192.168.100.78/1521;zdate

2019/02/11 09:36:14

2019/02/11 09:36:15

--//OK現在需要1秒.

--//一般以前使用nc或者telnet判斷,連結如下:

# echo a | nc -w 1 -n -v 192.168.xxx.xx 1-1521 2>/dev/null | grep "succeeded"

--//參考連結:http://blog.itpub.net/267265/viewspace-2148257/

--//關於INBOUND_CONNECT_TIMEOUT的設定,在sqlnet.ora與listener.ora意義不一樣,一個表示等待使用者認證超時的時間,一個表示等待用

--//戶連線請求超時的時間. 可以參考我以前連結:

--// http://blog.itpub.net/267265/viewspace-2147529/

3.自己在重複驗證看看.

$ grep INBOUND_CONNECT_TIMEOUT sqlnet.ora listener.ora

sqlnet.ora:SQLNET.INBOUND_CONNECT_TIMEOUT=30

listener.ora:INBOUND_CONNECT_TIMEOUT_LISTENER=1

$ ps -ef | grep oracleboo[k]

--//沒有任何輸出.也就是遠端沒有客戶連線伺服器.

$ zdate;sqlplus scott/xxxxx@book

2019/02/11 09:48:04

SQL*Plus: Release 11.2.0.4.0 Production on Mon Feb 11 09:48:04 2019

ERROR:

ORA-01017: invalid username/password; logon denied

--//注意sqlplus不能使用-l引數,不然馬上退出了.

--//切換終端會話,執行如下:

$ ps -ef | grep oracleboo[k]

oracle 43849 1 0 09:48 ? 00:00:00 oraclebook (LOCAL=NO)

--//可以發現實際上網路連線已經建立.

--//等alert*.log出現如下資訊,在取消上面sqlplus的執行:

--//alert.log

Mon Feb 11 09:48:34 2019

WARNING: inbound connection timed out (ORA-3136)

--//兩者時間相減就是30秒.這個引數也就是sqlnet.ora有關.也就是等待使用者認證超時的時間.

$ zdate ;cat < /dev/tcp/192.168.100.78/1521;zdate

2019/02/11 10:00:21

2019/02/11 10:00:22

--//正好1秒,這個時候就是表示等待使用者連線請求超時的時間.

$ zdate; telnet 192.168.100.78 1521;zdate

2019/02/11 10:01:38

Trying 192.168.100.78...

Connected to xxxxxdg4.com (192.168.100.78).

Escape character is '^]'.

Connection closed by foreign host.

2019/02/11 10:01:39

$ time telnet 192.168.100.78 1521

Trying 192.168.100.78...

Connected to xxxxxdg4.com (192.168.100.78).

Escape character is '^]'.

Connection closed by foreign host.

real 0m1.007s

user 0m0.001s

sys 0m0.003s

$ /usr/bin/time -p telnet 192.168.100.78 1521 > /dev/null

Connection closed by foreign host.

Command exited with non-zero status 1

real 1.00

user 0.00

sys 0.00

[20190211]簡單測試埠是否開啟.txt

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