feat: add test code of 1 million tcp connection

tests/network/test03/java/Client.java

@@ -0,0 +1,53 @@
+import java.net.Socket;
+import java.net.InetSocketAddress;
+ 
+public class Client {
+    public static final int MAX_CONNECTION_NUM = 50000;
+
+    public static void main(String[] args) throws Exception {
+        if(2 != args.length){
+            System.out.println("Usage: java Client <server ip> <server port>\n");
+            return;
+        }
+
+        //1. 从命令行获取并解析local ip、server ip以及端口
+        String sIp = args[0];
+        int sPort = Integer.parseInt(args[1]);
+
+        //2. 开始建立连接
+        //用数组将 socket 保存起来，防止连接被过早释放
+        Socket[] sockets = new Socket[MAX_CONNECTION_NUM];  
+        for(int i = 1; i <= MAX_CONNECTION_NUM; i++){
+            try {
+                Socket s = new Socket();
+                s.connect(new InetSocketAddress(sIp, sPort));
+
+                if(false == s.isConnected()){
+                    System.out.println(" 连接 "+sIp+":"+sPort+" 失败！ ");
+                    return;
+                }
+                sockets[i-1] = s;
+
+            } catch (Exception e) {
+                //连接失败则小憩一会儿接着连
+                Thread.sleep(500);
+                e.printStackTrace();
+            }
+
+            //稍稍停顿一下，避免把服务端的握手队列打满
+            if(0 == i % 500){
+                Thread.sleep(500);
+                System.out.println("连接 "+sIp+":"+sPort+" 成功了 "+i+" 条");
+            }
+        }
+      
+        //把所有连接都 hold 一会儿，方便观察
+        Thread.sleep(300 * 1000);
+
+        //3. 释放所有的连接
+        System.out.println("关闭所有的连接...\n");
+        for(int i = 0; i < MAX_CONNECTION_NUM; i++){
+            sockets[i].close();
+        }
+   }
+}