怎样检测TCP/UDP端口的连通性

TCP端口的连通性

方法一：TCP协议是面向连接的，可以直接通过telnet命令连接

telent ip port 

➜  packages telnet 127.0.0.1 80
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.

方法二：使用nc（netcat）命令

nc -vz ip port 

➜  packages nc -vz 127.0.0.1 80
found 0 associations
found 1 connections:
     1: flags=82<CONNECTED,PREFERRED>
    outif lo0
    src 127.0.0.1 port 49594
    dst 127.0.0.1 port 80
    rank info not available
    TCP aux info available

Connection to 127.0.0.1 port 80 [tcp/http] succeeded!

➜  packages nc -zv 127.0.0.1 8080
nc: connectx to 127.0.0.1 port 8080 (tcp) failed: Connection refused

nc相关option:

        -u      UDP mode
        -v      Verbose
        -z      Zero-I/O mode [used for scanning]

UDP端口的连通性

UDP协议是无连接的，不需要握手建立连接，数据发送后，server端也不会返回确认信息。

方法一：使用nc(netcat)命令

nc -uvz ip port

➜  packages nc -uvz 127.0.0.1 80
found 0 associations
found 1 connections:
     1: flags=82<CONNECTED,PREFERRED>
    outif (null)
    src 127.0.0.1 port 54152
    dst 127.0.0.1 port 80
    rank info not available

Connection to 127.0.0.1 port 80 [udp/http] succeeded!

总结：nc(netcat)是专门用于TCP/UDP连接和监听的命令，建议大家直接使用nc。