以80端口为例解答
法一：此法常被用来检测是个远端端口是否通畅
1 [root@oldboy ~]# telnet baidu.com 80 2 Trying 123.125.114.144... 3 Connected to baidu.com (123.125.114.144). #==>出现Connected表示连通了，说明百度的80端口开放的 4 Escape character is ‘^]‘. #==>ctrl+]退出此地。 5 ^] 6 telnet> quit 7 Connection closed.
如果写脚本通过telnet检查端口可以用下面的方法：
1 [root@oldboy ~]# echo -e "\n"|telnet baidu.com 80|grep Connected 2 Connection closed by foreign host. 3 Connected to baidu.com (123.125.114.144).
法二：通过nmap来检查端口是否通畅
1 [root@oldboy ~]# nmap etiantian.org -p 80 2 Starting Nmap 4.11 ( http://www.insecure.org/nmap/ ) at 2012-07-22 17:22 PDT 3 Interesting ports on 211.100.98.99: 4 PORT STATE SERVICE 5 80/tcp open http 6 Nmap finished: 1 IP address (1 host up) scanned in 0.417 seconds
如果写脚本通过nmap检查端口可以用下面的方法：
1 26 PORT_COUNT=`nmap $ip_add -p $port|grep open|wc -l` 2 29 [[ $PORT_COUNT -ge 1 ]] && echo "$ip_add $port is ok." || echo "$ip_add $port is unknown."
法三：通过nc命令检查
1 [root@oldboy ~]# nc -w 5 211.100.98.99 80 && echo ok 2 ok 3 [root@oldboy ~]# nc -w 10 8.8.8.8 53 && echo ok ||echo no 4 ok
如果写脚本通过nc检查端口并监控memcache服务可以用下面的方法：
1 export oldboyTimestampMemcachedIp=$1 2 export oldboyTimestampMemcachedPort=$2 3 export oldboyTitle=NAGIOS 4 export oldboyTimestampMD5=4ED06F8D41B9264OLD0BOY30BE5212BB7E34 5 export wwwServerIp=$3 6 export wwwServerPort=$4 7 8 printf "delete $oldboyTimestampMD5\r\n" | nc $oldboyTimestampMemcachedIp $oldboyTimestampMemcachedPort >/dev/null 2>&1 9 sleep 1 10 judge=($(printf "HEAD /oldboy/$oldboyTitle HTTP/1.1\r\nHost: $5\r\n\r\n" | nc $wwwServerIp $wwwServerPort | head -n1|tr "\r" "\n"))
本文出自 “老男孩linux培训” 博客，请务必保留此出处http://oldboy.blog.51cto.com/2561410/942530
原文：http://www.cnblogs.com/sunfie/p/5149089.html