1.Ping是Windows、Unix和Linux系统下的一个命令。

ping也属于一个通信协议，是TCP/IP协议的一部分。

利用“ping”命令可以检查网络是否连通，可以很好地帮助我们分析和判定网络故障。

Ping发送一个ICMP (Internet Control Messages Protocol）即因特网信报控制协议，回声请求消息给目的地并报告是否收到所希望的 ICMP  echo （ICMP回声应答），用来检查网络是否通畅或者网络连接速度的命令。广义来说即发送一个数据包，根据返回的数据包得到丢包率及平均时间得出网络的连接状态。 ping命令可以用在android中检测网络ip或者socket的连接，命令格式：ping ip地址（最简） ping具有一些参数，可以具体定义包的个数、包的最大存活时间等

2.具体参数：

参数详解-aAudible ping.-A自适应ping，根据ping包往返时间确定ping的速度；-b允许ping一个广播地址；-B不允许ping改变包头的源地址；-c countping指定次数后停止ping； -d 使用Socket的SO_DEBUG功能；-F flow_label为ping回显请求分配一个20位的“flow label”，如果未设置，内核会为ping随机分配；-f极限检测，快速连续ping一台主机，ping的速度达到100次每秒；-i interval设定间隔几秒发送一个ping包，默认一秒ping一次；-I interface指定网卡接口、或指定的本机地址送出数据包；-l preload设置在送出要求信息之前，先行发出的数据包；-L抑制组播报文回送，只适用于ping的目标为一个组播地址-n 不要将ip地址转换成主机名；-p pattern指定填充ping数据包的十六进制内容，在诊断与数据有关的网络错误时这个选项就非常有用，如：“-p ff”；-q不显示任何传送封包的信息，只显示最后的结果-Q tos设置Qos(Quality of Service)，它是ICMP数据报相关位；可以是十进制或十六进制数，详见rfc1349和rfc2474文档；-R记录ping的路由过程(IPv4 only)；注意：由于IP头的限制，最多只能记录9个路由，其他会被忽略；-r忽略正常的路由表，直接将数据包送到远端主机上，通常是查看本机的网络接口是否有问题；如果主机不直接连接的网络上，则返回一个错误。-S sndbufSet socket sndbuf. If not specified, it is selected to buffer not more than one packet.-s packetsize指定每次ping发送的数据字节数，默认为“56字节”+“28字节”的ICMP头，一共是84字节；包头+内容不能大于65535，所以最大值为65507（linux:65507, windows:65500）；-t ttl设置TTL(Time To Live)为指定的值。该字段指定IP包被路由器丢弃之前允许通过的最大网段数；-T timestamp_option设置IP timestamp选项,可以是下面的任何一个：　　'tsonly' (only timestamps)　　'tsandaddr' (timestamps and addresses)　　'tsprespec host1 [host2 [host3]]' (timestamp prespecified hops). -M hint 设置MTU（最大传输单元）分片策略。可设置为：　　'do'：禁止分片，即使包被丢弃；　　'want'：当包过大时分片；　　'dont'：不设置分片标志（DF flag）；-m mark设置mark；-v使ping处于verbose方式，它要ping命令除了打印ECHO-RESPONSE数据包之外，还打印其它所有返回的ICMP数据包；-U Print full user-to-user latency (the old behaviour).Normally ping prints network round trip time, which can be different f.e. due to DNS failures.-W timeout以毫秒为单位设置ping的超时时间；-w deadlinedeadline； 当然，这只是个小的例子，结合上面给的参数，你爱ping什么ping什么。

3.Runtime.exec()：

ping这个命令其实也没什么可说的，主要想再说说Runtime.exec()方法，这个方法不单纯只是Ping，其实他能完成几乎所有的Linux命令结果 还有Process类，顾名思义Process进程（Process）是计算机中的程序关于某数据集合上的一次运行活动，是系统进行资源分配和调度的基本单位，是操作系统结构的基础。 这个类，有获取读写流的方法，就说明我们刚才的exec会以流的方式返回结果。

3.1.Runtime

好，最后重点说一下Runtime，他在java.lang包下面，

/** * Executes the specified command and its arguments in a separate native * process. The new process inherits the environment of the caller. Calling * this method is equivalent to calling {@code exec(progArray, null, null)}. * * @param progArray * the array containing the program to execute as well as any * arguments to the program. * @return the new {@code Process} object that represents the native * process. * @throws IOException * if the requested program can not be executed. */ public Process exec(String[] progArray) throws java.io.IOException { return exec(progArray, null, null); } /** * Executes the specified command and its arguments in a separate native * process. The new process uses the environment provided in {@code envp}. * Calling this method is equivalent to calling * {@code exec(progArray, envp, null)}. * * @param progArray * the array containing the program to execute as well as any * arguments to the program. * @param envp * the array containing the environment to start the new process * in. * @return the new {@code Process} object that represents the native * process. * @throws IOException * if the requested program can not be executed. */ public Process exec(String[] progArray, String[] envp) throws java.io.IOException { return exec(progArray, envp, null); } /** * Executes the specified command and its arguments in a separate native * process. The new process uses the environment provided in {@code envp} * and the working directory specified by {@code directory}. * * @param progArray * the array containing the program to execute as well as any * arguments to the program. * @param envp * the array containing the environment to start the new process * in. * @param directory * the directory in which to execute the program. If {@code null}, * execute if in the same directory as the parent process. * @return the new {@code Process} object that represents the native * process. * @throws IOException * if the requested program can not be executed. */ public Process exec(String[] progArray, String[] envp, File directory) throws IOException { // ProcessManager is responsible for all argument checking. return ProcessManager.getInstance().exec(progArray, envp, directory, false); } /** * Executes the specified program in a separate native process. The new * process inherits the environment of the caller. Calling this method is * equivalent to calling {@code exec(prog, null, null)}. * * @param prog * the name of the program to execute. * @return the new {@code Process} object that represents the native * process. * @throws IOException * if the requested program can not be executed. */ public Process exec(String prog) throws java.io.IOException { return exec(prog, null, null); } /** * Executes the specified program in a separate native process. The new * process uses the environment provided in {@code envp}. Calling this * method is equivalent to calling {@code exec(prog, envp, null)}. * * @param prog * the name of the program to execute. * @param envp * the array containing the environment to start the new process * in. * @return the new {@code Process} object that represents the native * process. * @throws IOException * if the requested program can not be executed. */ public Process exec(String prog, String[] envp) throws java.io.IOException { return exec(prog, envp, null); } /** * Executes the specified program in a separate native process. The new * process uses the environment provided in {@code envp} and the working * directory specified by {@code directory}. * * @param prog * the name of the program to execute. * @param envp * the array containing the environment to start the new process * in. * @param directory * the directory in which to execute the program. If {@code null}, * execute if in the same directory as the parent process. * @return the new {@code Process} object that represents the native * process. * @throws IOException * if the requested program can not be executed. */ public Process exec(String prog, String[] envp, File directory) throws java.io.IOException { // Sanity checks if (prog == null) { throw new NullPointerException("prog == null"); } else if (prog.isEmpty()) { throw new IllegalArgumentException("prog is empty"); } // Break down into tokens, as described in Java docs StringTokenizer tokenizer = new StringTokenizer(prog); int length = tokenizer.countTokens(); String[] progArray = new String[length]; for (int i = 0; i < length; i++) { progArray[i] = tokenizer.nextToken(); } // Delegate return exec(progArray, envp, directory); }

prog时需要执行的程序，怎么理解，其实很简单，就是系统的command命令，到这大家应该都清楚了，Android是Linux系统，这里的指令也就是Linux的命令了，例如ps（查看进程），ls，pwd（查看现在路径，文件等等）等等，大家都可以去试试。

*注意点：

    1、exec的String prog只能执行一条指令，如果需要执行多条指令需要放入sh脚本文件中执行或者调用多次exec函数。

    2、exec的String command不支持通配符（*）。

    3、有些指令需要指定File dir（工作目录）。

    4、默认的工作目录是根目录/。（通过执行指令pwd可查到）

    5、导出logcat日志到SD卡ziyouku目录，参数：("logcat -df logcat.log",new File("/mnt/sdcard/ziyouku/"))

    6、logcat读取权限：<uses-permission android:name="android.permission.READ_LOGS" />

好，今天就说这么多，最近在做Spingboot开发后台并发系统，所以写博客也是对之前项目的很多技术点的总结完善。