对于web服务的开启的判断有以下几种常用方法：

1、端口查看：

本地：ss，netstat，lsof

示例一：
ss：查看80端口是否处于监听状态
[root@gw oldboy]# ss -an|grep 80
LISTEN     0      511                      :::80                      :::*
示例二：
netstat：查看80端口/httpd服务是否开启
[root@gw oldboy]# netstat -lntup|grep 80
tcp        0      0 :::80                       :::*                LISTEN      2317/httpd
[root@gw oldboy]# netstat -lntup|grep httpd
tcp        0      0 :::80                       :::*                LISTEN      2317/httpd
示例三：
lsof：查看80端口是否处于
[root@gw oldboy]# lsof -i :80
COMMAND  PID   USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
httpd   2317   root    4u  IPv6  13199      0t0  TCP *:http (LISTEN)
httpd   2320 apache    4u  IPv6  13199      0t0  TCP *:http (LISTEN)
httpd   2321 apache    4u  IPv6  13199      0t0  TCP *:http (LISTEN)
httpd   2322 apache    4u  IPv6  13199      0t0  TCP *:http (LISTEN)
httpd   2323 apache    4u  IPv6  13199      0t0  TCP *:http (LISTEN)
httpd   2324 apache    4u  IPv6  13199      0t0  TCP *:http (LISTEN)
httpd   2325 apache    4u  IPv6  13199      0t0  TCP *:http (LISTEN)
httpd   2326 apache    4u  IPv6  13199      0t0  TCP *:http (LISTEN)
httpd   2327 apache    4u  IPv6  13199      0t0  TCP *:http (LISTEN)

远程：nmap

示例一：
nmap：检测端口开启状态
[root@niaoyun ~]# nmap 192.168.1.21 -p 80Starting Nmap 5.51 ( http://nmap.org ) at 2015-08-30 21:59 CST
Nmap scan report for 192.168.1.21
Host is up (0.00013s latency).
PORT   STATE  SERVICE
80/tcp closed http     <== 注意这里
MAC Address: 00:0C:29:19:FC:7D (VMware)Nmap done: 1 IP address (1 host up) scanned in 0.10 seconds

2、本地进程数：

[root@niaoyun ~]# ps -ef|grep httpd
root       1249      1  0 22:05 ?        00:00:00 /usr/sbin/httpd
apache     1251   1249  0 22:05 ?        00:00:00 /usr/sbin/httpd
apache     1252   1249  0 22:05 ?        00:00:00 /usr/sbin/httpd
apache     1253   1249  0 22:05 ?        00:00:00 /usr/sbin/httpd
apache     1254   1249  0 22:05 ?        00:00:00 /usr/sbin/httpd
apache     1255   1249  0 22:05 ?        00:00:00 /usr/sbin/httpd
apache     1256   1249  0 22:05 ?        00:00:00 /usr/sbin/httpd
apache     1257   1249  0 22:05 ?        00:00:00 /usr/sbin/httpd
apache     1258   1249  0 22:05 ?        00:00:00 /usr/sbin/httpd
root       1260   1117  0 22:05 pts/0    00:00:00 grep httpd
[root@niaoyun ~]# ps -ef|grep httpd|wc -l
10

3、header状态值：

[root@niaoyun ~]# curl -I 192.168.1.20
HTTP/1.1 200 OK
Date: Sun, 30 Aug 2015 14:16:55 GMT
Server: Apache/2.2.15 (CentOS)
Last-Modified: Sun, 30 Aug 2015 14:16:23 GMT
ETag: "5fda3-13-51e87f62ea815"
Accept-Ranges: bytes
Content-Length: 19
Connection: close
Content-Type: text/html; charset=UTF-8
[root@niaoyun ~]# curl -I -s 192.168.1.20|head -1
HTTP/1.1 200 OK

4、URL（wget，curl）模拟用户的方式：

示例一：
wget：爬虫测试
[root@niaoyun ~]# wget --spider --timeout=10 192.168.1.20
Spider mode enabled. Check if remote file exists.
--2015-08-30 22:23:34--  http://192.168.1.20/
Connecting to 192.168.1.20:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 19 [text/html]
Remote file exists and could contain further links,
but recursion is disabled -- not retrieving.