目录:
- 使用bash和
timeout
- 使用
nc
- 命令
- RHEL 6 (nc-1.84)
- RHEL 7 (nmap-ncat-6.40)
- 备注
使用bash和timeout
:
请注意,timeout
应该在RHEL 6+中存在,或者在GNU coreutils 8.22中找到。在MacOS上,使用brew install coreutils
进行安装,并将其用作gtimeout
。
命令:
$ timeout $TIMEOUT_SECONDS bash -c "</dev/tcp/${HOST}/${PORT}"; echo $?
如果参数化主机和端口,请确保将它们指定为
${HOST}
和
${PORT}
,就像上面那样。不要仅仅指定它们为
$HOST
和
$PORT
,即没有大括号;在这种情况下这是不起作用的。
示例:
成功:
$ timeout 2 bash -c "</dev/tcp/canyouseeme.org/80"; echo $?
0
失败:
$ timeout 2 bash -c "</dev/tcp/canyouseeme.org/81"; echo $?
124
如果你必须要保留bash
的退出状态,
$ timeout --preserve-status 2 bash -c "</dev/tcp/canyouseeme.org/81"; echo $?
143
使用 nc
:
请注意,RHEL 7 上安装的 nc
版本不兼容之前版本。
命令:
请注意,下面的命令在 RHEL 6 和 7 中完全相同,只是安装和输出不同。
$ nc -w $TIMEOUT_SECONDS -v $HOST $PORT </dev/null; echo $?
RHEL 6 (nc-1.84):
安装:
$ sudo yum install nc
示例:
$ nc -w 2 -v canyouseeme.org 80 </dev/null; echo $?
Connection to canyouseeme.org 80 port [tcp/http] succeeded!
0
$ nc -w 2 -v canyouseeme.org 81 </dev/null; echo $?
nc: connect to canyouseeme.org port 81 (tcp) timed out: Operation now in progress
1
如果主机名映射到多个IP,则上述失败命令将循环遍历其中的许多或所有IP。例如:
$ nc -w 2 -v microsoft.com 81 </dev/null; echo $?
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
1
RHEL 7 (nmap-ncat-6.40):
安装:
$ sudo yum install nmap-ncat
例子:
$ nc -w 2 -v canyouseeme.org 80 </dev/null; echo $?
Ncat: Version 6.40 ( http://nmap.org/ncat )
Ncat: Connected to 52.202.215.126:80.
Ncat: 0 bytes sent, 0 bytes received in 0.22 seconds.
0
$ nc -w 2 -v canyouseeme.org 81 </dev/null; echo $?
Ncat: Version 6.40 ( http://nmap.org/ncat )
Ncat: Connection timed out.
1
如果主机名映射到多个IP地址,上述失败命令将循环遍历其中的许多或全部IP地址。例如:
$ nc -w 2 -v microsoft.com 81 </dev/null; echo $?
Ncat: Version 6.40 ( http://nmap.org/ncat )
Ncat: Connection to 104.43.195.251 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection to 23.100.122.175 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection to 23.96.52.53 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection to 191.239.213.197 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection timed out.
1
备注:
-v
(--verbose
)参数和echo $?
命令仅用于说明作用。