我正在使用RabbitMq 3.6.6和paho. mqttv3协议，我的简单代码如下

int max_connections =400000;
String broker = "tcp://xxx.xxx.x.xx:1883";
String clientId = "Publisher";
String content="Hii";
int qos=1;
String topic="Cluster";


MemoryPersistence persistence = new MemoryPersistence();
MqttClient sampleClient[] = new MqttClient[max_connections];

Thread t[] = new Thread[max_connections];
MqttConnectOptions connOpts = new MqttConnectOptions();
connOpts.setCleanSession(true);

for (int i = 0; i < max_connections; i++) {
    try {
        sampleClient[i] = new MqttClient(broker, clientId + "" + i, persistence);
        sampleClient[i].connect(connOpts);
    } catch (MqttException ex) {
        ex.printStackTrace();
        return;
    } 
}

我得到了例外，比如：

线程"MQTT Con： Publisher2919"java.lang.OutOfMemoryError中的异常：无法在java.lang.Thread.start 0（本机方法）在java.lang.Thread.start（Thread.java:714）在org.eclipse.paho.client.mqttv3.interal.CommsSender.start（CommsSender.java:60）在org.eclipse.paho.client.mqttv3.interal.ClientComms$ConnectBG.run（ClientComms.java:654）在java.lang.Thread.run（Thread.java:745）

我的系统RAM是8 GB与Corei5处理器。

我也尝试在WindowsPC在相同的错误，但其高达7k连接

so any OS level Configuration in Ubuntu to make more Connection?