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A common way to measure network latency to a remote host is to use the ping
application. The ping
tool relies on ICMP ECHO request and reply packets to measure the round-trip latency of the remote host. However, in some cases, ICMP traffic may be blocked by a firewall, making the ping
application useless for hosts behind restricted firewalls. In this case, you will need to rely on layer 3 measurement tools that use TCP/UDP packets, as these layer 3 packets are more likely to bypass common firewall rules.
One such layer 3 measurement tool is tcpping
. To measure latency, tcpping
utilizes the so-called semi-open connection technology
, based on TCP three-way handshake. That is, it sends a TCP SYN packet to the remote host via the port number (default is 80). If the remote host is listening on that port, it will respond with a TCP ACK packet. Otherwise, it will respond with a TCP RST packet. Either way, tcpping
can measure the round-trip time (RTT) latency of the remote host by timing outgoing SYN packets and incoming ACK (or RST) packets.
tcpping
tcpping
Implemented as a shell script that responds to external tools to perform and report RTT measurements. Therefore, in order to install tcpping
, you first need to install these prerequisites.
tcptraceroute
To install on Ubuntu or Debiantcptraceroute
:
$ sudo apt-get install tcptraceroute
To install tcptraceroute
on CentOS or RHEL, first set up RepoForge on your system, then run:
$ sudo yum install tcptraceroute
bc
使用的另一个工具tcpping
是GNUbc
,它预装在所有主要的 Linux 发行版上。但是,如果你tcpping
在最小 Linux 运行时环境(例如Docker容器、AWS 最小映像 AMI)中运行,则bc
可能不会预先安装。在这种情况下,你需要bc
自己安装。
在Debian 的 Linux 上安装:
$ sudo apt-get install bc
在 Red Hat 的 Linux 上安装:
$ sudo yum install bc
tcpping
安装这些必备工具后,最后继续tcpping
从官方源下载。
$ wget http://www.vdberg.org/~richard/tcpping $ cp tcpping /usr/bin $ chmod 755 tcpping
tcpping
来衡量延迟要使用 测量网络延迟tcpping
,你可以使用以下格式。
tcpping [-d] [-c] [-r sec] [-x count] ipaddress [端口]
-d
: 在每个结果之前打印时间戳。-c
: 使用分列输出以便于解析。-r
:连续探测之间的间隔(以秒为单位)(默认为 1 秒)。-x
: 重复 n 次(默认无限制)。[port]
: 目标端口(默认为 80)。请注意,你需要 root 权限才能运行,tcpping
因为它需要调用特权tcptraceroute
命令。
对于任何开放 80 端口的目标 Web 服务器,你可以使用以下方法测量其 RTT 延迟tcpping
。
tcpping www.rumenz.com seq 0: tcp response from 42.194.162.109 (42.194.162.109) 33.822 ms traceroute to rumenz.com (42.194.162.109), 255 hops max, 60 byte packets seq 1: tcp response from 42.194.162.109 (42.194.162.109) 33.975 ms traceroute to rumenz.com (42.194.162.109), 255 hops max, 60 byte packets seq 2: tcp response from 42.194.162.109 (42.194.162.109) 32.010 ms traceroute to rumenz.com (42.194.162.109), 255 hops max, 60 byte packets seq 3: tcp response from 42.194.162.109 (42.194.162.109) 32.209 ms traceroute to rumenz.com (42.194.162.109), 255 hops max, 60 byte packets seq 4: tcp response from 42.194.162.109 (42.194.162.109) 30.866 ms traceroute to rumenz.com (42.194.162.109), 255 hops max, 60 byte packets seq 5: tcp response from 42.194.162.109 (42.194.162.109) 34.866 ms traceroute to rumenz.com (42.194.162.109), 255 hops max, 60 byte packets seq 6: tcp response from 42.194.162.109 (42.194.162.109) 32.604 ms traceroute to rumenz.com (42.194.162.109), 255 hops max, 60 byte packets seq 7: tcp response from 42.194.162.109 (42.194.162.109) 30.495 ms
对于任意远程主机,在运行tcpping
. 要检查远程 TCP 端口是否打开,你可以使用nc
如下命令。
$ nc -vn
-t
: 连续 TCPing ,直到使用 Ctrl+C 键停止tcping -t 1.1.1.1 80
-n 5
: TCPing 5次后停止tcping -i 5 1.1.1.1 80
-w 0.5
: 设置超时时间为 0.5秒(1秒=1000毫秒),单位 秒tcping -w 0.5 1.1.1.1 80
-d
:在每行返回信息中加入时间信息tcping -d 1.1.1.1 80
-s
: 当 TCPing 测试成功后(在超时时间以内返回 TCPing 延迟数据)自动停止 TCPingtcping -s 1.1.1.1 80
-4
: 优先 IPv4(如果一个域名有 IPv4 和 IPv6 解析,那么走 IPv4)tcping -s 1.1.1.1 80
-6
:优先 IPv6(如果一个域名有 IPv4 和 IPv6 解析,那么走 IPv6)tcping -6 www.rumenz.com 80
--file
: TCPing 将逐行循环遍历文件内的 服务器IP/域名 信息(一行一个,支持端口,例如:1.1.1.1 443)tcping --file rumenz.txt
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