nmap 扫描端口时候 Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn Nmap done: 1 IP address (0 hosts up) scanned in 0.50 seconds

这个提示意味着nmap无法检测到目标主机的响应，可能是因为主机已关闭或被防火墙阻止了ping探测。您可以尝试使用`-Pn`选项来禁用ping探测，这样nmap将使用其他方法来确定主机是否在线。例如，您可以使用以下命令：

nmap -Pn <target_ip>

如果目标主机确实在线但阻止了ping，则此命令应该能够扫描到目标主机的开放端口。

相关问题

nmap -v scanme.nmap.org 扫描与 nmap -vv scanme.nmap.org 扫描的区别是什么

根据提供的引用[1]，nmap是一款网络探测和安全审计工具。使用-v选项可以增加扫描的详细程度，使用-vv选项可以进一步增加详细程度。因此，nmap -v scanme.nmap.org扫描的详细程度比nmap -vv scanme.nmap.org扫描的详细程度要少。

下面是两个命令的示例：

1. nmap -v scanme.nmap.org扫描的输出示例：

Starting Nmap 7.80 ( https://nmap.org ) at 2021-08-17 09:30 PDT
Initiating Ping Scan at 09:30
Scanning scanme.nmap.org (45.33.32.156) [2 ports]
Completed Ping Scan at 09:30, 0.00s elapsed (1 total hosts)
Initiating Parallel DNS resolution of 1 host. at 09:30
Completed Parallel DNS resolution of 1 host. at 09:30, 0.02s elapsed
Initiating Connect Scan at 09:30
Scanning scanme.nmap.org (45.33.32.156) [1000 ports]
Discovered open port 80/tcp on 45.33.32.156
Discovered open port 22/tcp on 45.33.32.156
Completed Connect Scan at 09:30, 0.11s elapsed (1000 total ports)
Nmap scan report for scanme.nmap.org (45.33.32.156)
Host is up (0.11s latency).
Other addresses for scanme.nmap.org (not scanned): 2600:3c03::f03c:91ff:fe18:bb2f
Not shown: 998 filtered ports
PORT   STATE SERVICE
22/tcp open  ssh
80/tcp open  http

Read data files from: /usr/bin/../share/nmap
Nmap done: 1 IP address (1 host up) scanned in 0.18 seconds

2. nmap -vv scanme.nmap.org扫描的输出示例：

Starting Nmap 7.80 ( https://nmap.org ) at 2021-08-17 09:31 PDT
Initiating Ping Scan at 09:31
Scanning scanme.nmap.org (45.33.32.156) [2 ports]
Packet capture filter (device eth0): icmp and ((ip[20:2] - ip[16:2]) - ((ip[0]&0xf)<<2)) != 0
Completed Ping Scan at 09:31, 0.00s elapsed (1 total hosts)
Initiating Parallel DNS resolution of 1 host. at 09:31
Completed Parallel DNS resolution of 1 host. at 09:31, 0.02s elapsed
Initiating Connect Scan at 09:31
Scanning scanme.nmap.org (45.33.32.156) [1000 ports]
Discovered open port 80/tcp on 45.33.32.156
Discovered open port 22/tcp on 45.33.32.156
Completed Connect Scan at 09:31, 0.11s elapsed (1000 total ports)
Nmap scan report for scanme.nmap.org (45.33.32.156)
Host is up, received syn-ack (0.11s latency).
Other addresses for scanme.nmap.org (not scanned): 2600:3c03::f03c:91ff:fe18:bb2f
Not shown: 998 filtered ports
Reason: 998 no-responses and 2 host-prohibited
PORT   STATE SERVICE REASON
22/tcp open  ssh     syn-ack ttl 56
80/tcp open  http    syn-ack ttl 56

Read data files from: /usr/bin/../share/nmap
Nmap done: 1 IP address (1 host up) scanned in 0.18 seconds

bash: nmap: command not found...

您的系统似乎没有安装nmap命令。nmap是一个用于网络探测和安全评估的工具。要解决这个问题，您可以尝试以下方法之一：

1. 如果您使用的是Linux系统，请确保已经安装了nmap软件包。您可以打开终端，并运行以下命令来安装nmap：

   sudo apt-get install nmap

2. 如果您使用的是Mac系统，请确保已经安装了Homebrew包管理器。然后在终端中运行以下命令来安装nmap：

   brew install nmap

3. 如果您使用的是Windows系统，请从nmap官方网站（https://nmap.org/）下载并安装适用于Windows的nmap版本。

请注意，如果您不具备系统管理员权限，可能无法安装软件包。在这种情况下，您可以尝试使用可移植版本的nmap或者联系系统管理员进行安装。