Java simple code: java.net.SocketException: Unexpected end of file from server

Question

I wrote some simple code in Java, the method should connect to the website and return the BufferedReader.

private BufferedReader getConnection(String url_a) {
        URL url;
        try {
            System.out.println("getting connection");
            url = new URL(url_a);
            HttpURLConnection urlConnection = (HttpURLConnection) 
                     url.openConnection();
            urlConnection.addRequestProperty("User-Agent",
                    "Mozilla/5.0 (X11; U; Linux i586; en-US; rv:1.7.3) Gecko/20040924"
                     + "Epiphany/1.4.4 (Ubuntu)");
            inStream = new InputStreamReader(urlConnection.getInputStream());
            return new BufferedReader(inStream);
        } catch (Exception ex) {
            Logger.getLogger(Reader.class.getName()).log(Level.SEVERE, null, ex);
        }
        return null;

}

When I use it on my PC, it works fine but when I put .jar file on the server I get this error:

java.net.SocketException: Unexpected end of file from server
at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:718)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:579)
at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:715)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:579)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1322)
at dataconverter.Reader.getConnection(Reader.java.260)

Problem is quite strange because the exception isn't thrown each time, sometimes everything is OK and program works fine.

Has anybody got any ideas?

Answer 1

"Unexpected end of file" implies that the remote server accepted and closed the connection without sending a response. It's possible that the remote system is too busy to handle the request, or that there's a network bug that randomly drops connections.

With the information available it's impossible to say what's going wrong. If you have access to the servers in question you can use packet sniffing tools to find what exactly is sent and received, and look at logs to of the server process to see if there are any error messages.

Answer 2

Summary

This exception is encountered when you are expecting a response, but the socket has been abruptly closed.

Detailed Explanation

Java's HTTPClient, found here, throws a SocketException with message "Unexpected end of file from server" in a very specific circumstance.

After making a request, HTTPClient gets an InputStream tied to the socket associated with the request. It then polls that InputStream repeatedly until it either:

1. Finds the string "HTTP/1."
2. The end of the InputStream is reached before 8 characters are read
3. Finds a string other than "HTTP/1."

In case of number 2, HTTPClient will throw this SocketException if any of the following are true:

• The HTTP method is CONNECT
• The HTTP method is POST and the client is set to streaming mode

Why would this happen

This indicates that the TCP socket has been closed before the server was able to send a response. This could happen for any number of reasons, but some possibilities are:

• Network connection was lost
• The server decided to close the connection
• Something in between the client and the server (nginx, router, etc) terminated the request

_{Note: When Nginx reloads its config, it forcefully closes any in-flight HTTP Keep-Alive connections (even POSTs), causing this exact error.}

Answer 3

I do get this error when I do not set the Authentication header or I set wrong credentials.

Answer 4

I would suggest using wire shark to trace packets. If you are using Ubuntu, sudo-apt get wireshark. Like Joni stated the only way to figure out whats going wrong is to follow the GET requests and their associated responses.

http://www.wireshark.org/download.html

Answer 5

In my case it was solved just passing proxy to connection. Thanks to @Andreas Panagiotidis.

Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("<YOUR.HOST>", 80)));
HttpsURLConnection con = (HttpsURLConnection) url.openConnection(proxy);

Answer 6

Most likely the headers you are setting is incorrect or not acceptable.

Example: connnection.setRequestProperty("content-type", "application/json");

Answer 7

I got this exception too. MY error code is below

        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestMethod(requestMethod);
        connection.setRequestProperty("Content-type", "JSON");

I found "Content-type" should not be "JSON",is wrong! I solved this exception by update this line to below

        connection.setRequestProperty("Content-type", "application/json");

you can check up your "Content-type"