Why would a “java.net.ConnectException: Connection

Question

I'm getting a ConnectException: Connection timed out with some frequency from my code. The URL I am trying to hit is up. The same code works for some users, but not others. It seems like once one user starts to get this exception they continue to get the exception.

Here is the stack trace:

java.net.ConnectException: Connection timed out
Caused by: java.net.ConnectException: Connection timed out
    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.Socket.connect(Socket.java:516)
    at java.net.Socket.connect(Socket.java:466)
    at sun.net.NetworkClient.doConnect(NetworkClient.java:157)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:365)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:477)
    at sun.net.www.http.HttpClient.<init>(HttpClient.java:214)
    at sun.net.www.http.HttpClient.New(HttpClient.java:287)
    at sun.net.www.http.HttpClient.New(HttpClient.java:299)
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:796)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:748)
    at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:673)
    at sun.net.www.protocol.http.HttpURLConnection.getOutputStream(HttpURLConnection.java:840)

Here is a snippet from my code:

URLConnection urlConnection = null;
OutputStream outputStream = null;
OutputStreamWriter outputStreamWriter = null;
InputStream inputStream = null;

try {
    URL url = new URL(urlBase);
    urlConnection = url.openConnection();
    urlConnection.setDoOutput(true);

    outputStream = urlConnection.getOutputStream(); // exception occurs on this line
    outputStreamWriter = new OutputStreamWriter(outputStream);
    outputStreamWriter.write(urlString);
    outputStreamWriter.flush();
    inputStream = urlConnection.getInputStream();
    String response = IOUtils.toString(inputStream);
    return processResponse(urlString, urlBase, response);
} catch (IOException e) {
    throw new Exception("Error querying url: " + urlString, e);
} finally {
    IoUtil.close(inputStream);
    IoUtil.close(outputStreamWriter);
    IoUtil.close(outputStream);
}

Answer 1

The error message says it all: your connection timed out. This means your request did not get a response within some (default) timeframe. The reasons that no response was received is likely to be one of:

a) The IP/domain or port is incorrect

b) The IP/domain or port (i.e service) is down

c) The IP/domain is taking longer than your default timeout to respond

d) You have a firewall that is blocking requests or responses on whatever port you are using

e) You have a firewall that is blocking requests to that particular host

f) Your internet access is down

g) Your live-server is down i.e in case of "rest-API call".

Note that firewalls and port or IP blocking may be in place by your ISP

Answer 2

I solved my problem with:

System.setProperty("https.proxyHost", "myProxy");
System.setProperty("https.proxyPort", "80");

or http.proxyHost...

Answer 3

There is a possibility that your IP/host are blocked by the remote host, especially if it thinks you are hitting it too hard.