Update nc.md

jaywcjlove · web-flow · commit b59034148084 · 2018-10-11T09:55:40.000+08:00
diff --git a/command/nc.md b/command/nc.md
@@ -60,4 +60,13 @@ TCP端口扫描
 y  //用户输入
 ```
 
+查看 443 端口是否被阻止
+
+```bash
+nc -vz acme-v02.api.letsencrypt.org 443 -w2
+# Ncat: Version 7.50 ( https://nmap.org/ncat )
+# Ncat: Connected to 23.77.214.183:443.
+# Ncat: 0 bytes sent, 0 bytes received in 0.07 seconds.
+```
+
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