大家都知道，测试网络延迟的命令是 ping，它是基于icmp协议测试两个主机之间的延迟，但是在实际应用中，发现很多服务器正常运行的情况下ping超时，这种情况我们通常会认为是服务器禁止了 icmp，禁止了ping，那么在这种情况下，我们想知道与目标服务器网络延迟该怎么办呢？有一个现成的方法，就是使用tcping，这是一个第三方开发的控制台程序，可以通过测试目标服务器开放的端口来获取tcp延迟。
【第一步】
在 https://elifulkerson.com/projects/tcping.php 下载 tcping.exe
【第二步】
将下载来的 tcping.exe 放到 C:\\Windows\\System32 目录；
之后你就可以在 CMD 命令模式下，输入：tcping www.baidu.com 80 来获取本地与目标服务器的网络延迟了。
参数设置（以下来自官方文档）：
NAME tcping - simulate \"ping\" over tcp by establishing a connection to network hosts. Measures the time for your system to [SYN], receive the target\'s [SYN][ACK] and send [ACK]. Note that the travel time for the last ACK is not included - only the time it takes to be put on the wire a tthe sending end. SYNOPSIS tcping [-tdsvf46] [-i interval] [-n times] [-w interval] [-b n] [-r times][-j depth] [--tee filename] [-f] destination [port] DESCRIPTION tcping measures the time it takes to perform a TCP 3-way handshake (SYN, SYN/ACK, ACK) between itself and a remote host. The travel time of the outgoing final ACK is not included, only the (minimal) amount of time it has taken to drop it on the wire at the near end. This allows the travel time of the (SYN, SYN/ACK) to approximate the travel time of the ICMP (request, response) equivalent. OPTIONS -4 Prefer using IPv4 -6 Prefer using IPv6 -t ping continuously until stopped via control-c -n count send _count_ pings and then stop. Default 4. -i interval Wait _interval_ seconds between pings. Default 1. Decimals permitted. -w interval Wait _interval_ seconds for a response. Default 2. Decimals permitted. -d include date and time on every output line -f Force sending at least one byte in addition to making the connection. -g count Give up after _count_ failed pings. -b type Enable audible beeps. \'-b 1\' will beep \"on down\". If a host was up, but now its not, beep. \'-b 2\' will beep \"on up\". If a host was down, but now its up, beep. \'-b 3\' will beep \"on change\". If a host was one way, but now its the other, beep. \'-b 4\' will beep \"always\". -c only show output on a changed state -r count Every _count_ pings, we will perform a new DNS lookup for the host in case it changed. -s Exit immediately upon a success. -v Print version and exit. -j Calculate jitter. Jitter is defined as the difference between the last response time and the historical average. -js depth Calculate jitter, as with -j but with an optional _depth_ argument specified. If _depth_ is specified tcping will use the prior _depth_ values to calculate a rolling average. --tee _filename_ Duplicate output to the _filename_ specified. Windows can still not be depended upon to have a useful command line environment. Don\'t tease me, *nix guys. --append When using --tee, append to rather than overwrite the output file. --file Treat the \"destination\" option as a filename. That file becomes a source of destinations, looped through on a line by line basis. Some options don\'t work in this mode and statistics will not be kept. destination A DNS name, an IP address, or (in \"http\" mode) a URL. Do not specify the protocol (\"http://\") in \"http\" mode. Also do not specify server port via \":port\" syntax. For instance: \"tcping http://www.elifulkerson.com:8080/index.html\" would fail Use the style: \"tcping www.elifulkerson.com/index.html 8080\" instead. port A numeric TCP port, 1-65535. If not specified, defaults to 80. --header include a header with the command line arguments and timestamp. Header is implied if using --tee. HTTP MODE OPTIONS -h Use \"http\" mode. In http mode we will attempt to GET the specified document and return additional values including the document\'s size, http response code, kbit/s. -u In \"http\" mode, include the target URL on each output line. --post Use POST instead of GET in http mode. --head Use HEAD instead of GET in http mode. --get Shorthand to invoke \"http\" mode for consistency\'s sake. --proxy-server _proxyserver_ Connect to _proxyserver_ to request the url rather than the server indicated in the url itself. --proxy-port _port_ Specify the numeric TCP port of the proxy server. Defaults to 3128. --proxy-credentials username:password Specify a username:password pair which is sent as a \'Proxy-Authorization: Basic\' header. RETURN VALUE tcping returns 0 if all pings are successful, 1 if zero pings are successful and 2 for mixed outcome. BUGS/REQUESTS Please report bugs and feature requests to the author via contact information on http://www.elifulkerson.com AVAILABILITY tcping is available at http://www.elifulkerson.com/projects/tcping.php
