Question

I am creating a test app to load test a comet servlet by creating a bunch of outbound https connections (each looping in its own thread).

Is there a limit on the number of concurrent outbound http requests? If so, is it an OS level issue (xp 32bit) or Java? I get the following exception when running around 100 connections. The error does not occur instantly but after anywhere between 50-150 loops (sometimes more), leading me to suspect that it actually might be me not releasing resources correctly:

java.net.BindException: Address already in use: connect
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
    at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
    at java.net.Socket.connect(Socket.java:529)
    at com.sun.net.ssl.internal.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:559)
    at         com.sun.net.ssl.internal.ssl.BaseSSLSocketImpl.connect(BaseSSLSocketImpl.java:141)
 at sun.net.NetworkClient.doConnect(NetworkClient.java:163)
 at sun.net.www.http.HttpClient.openServer(HttpClient.java:394)
 at sun.net.www.http.HttpClient.openServer(HttpClient.java:529)
 at sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:272)
 at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:329)
 at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:172)
 at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:916)
 at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:158)
 at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1177)
 at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:234)
 at fqexconnectiontesting.FQEXHttpClient.run(FQEXHttpClient.java:158)
 at java.lang.Thread.run(Thread.java:662)

My code:

while(true){
try{                    
connection =(HttpsURLConnection) url.openConnection();                    
connection.setDoOutput(true);
connection.setRequestProperty("keep-alive", "true");
connection.setRequestMethod("GET");
input = new DataInputStream( connection.getInputStream() ); 
b = new byte[4096];                    
totalBytes += input.read(b);                    
input.close();
b = null;         
connection.disconnect();                                        
connection = null;
Thread.sleep(100);
}

Any ideas appreciated.

Thanks,
Dazz

Answer 1

By default Java opens only up to 5 persistent connections to the same host.
But your code uses the disconnect() method which AFAIK prevents persistent connections.

You should better read the documentation about Persistent Connections. Take the sample code near the end for getting a fully working persistent connection.

May be this fixes your problem.