Android IOException with http... but it still works

Question

I am using the httpclient to talk to a web server, but I occasionally get an IOException, but the strange thing is, the command still makes it to the web server. In fact, I even usually get a valid data response back from the server, along with the IOException. How should I treat IOExceptions?

Here's my code in case it's something I'm doing wrong:

DefaultHttpClient client = new DefaultHttpClient();
CookieSyncManager.getInstance().startSync();
HttpContext localContext = new BasicHttpContext();

String password = db.getWebPassword();
String username = db.getWebUsername();

HttpGet httpGet = new HttpGet(url);

final HttpParams httpParams = client.getParams();

// try playing with the timesouts, but I don't think I know what I am doing...
HttpConnectionParams.setConnectionTimeout(httpParams, 5000);
HttpConnectionParams.setSoTimeout(httpParams, 5000);

Integer responseCode = 0;
try 
{
    HttpResponse execute;
    UsernamePasswordCredentials creds = new UsernamePasswordCredentials(username, password);
    client.getCredentialsProvider().setCredentials(new AuthScope(AuthScope.ANY_HOST, AuthScope.ANY_PORT), creds);
    execute = client.execute(httpGet);
    HttpEntity entity = execute.getEntity(); // often catches an IOException here     
    Log.d(MY_DEBUG_TAG, "Execute complete: " + entity.toString());
    responseCode = execute.getStatusLine().getStatusCode();
    Log.d(MY_DEBUG_TAG, "Response Code: " + responseCode);
    if (responseCode == 401)
    {
         response = "ERROR";
     Toast.ShowToast("Username/Password error.", pa);
    }

    InputStream content = execute.getEntity().getContent();

    Log.d(MY_DEBUG_TAG, "Reading response");
    BufferedReader buffer = new BufferedReader(
              new InputStreamReader(content));
    String s = "";
    while ((s = buffer.readLine()) != null) 
    {
         response += s;
    }
    // remove all html if possible
    response = android.text.Html.fromHtml(response).toString();
    Log.d(MY_DEBUG_TAG, "Response = " + response);
}
catch (ClientProtocolException e) 
{
     Log.e(MY_ERROR_TAG, "ClientProtocolException: " + e.getMessage());
     Toast.ShowToast("Error connecting to server.", pa);
}
catch (IOException e)
{
       Log.e(MY_ERROR_TAG, "IOException: " + e.getMessage());
     Toast.ShowToast("Error connecting to server.", pa);
}

Stack trace added as per request:

java.net.SocketTimeoutException
    at org.apache.harmony.luni.net.PlainSocketImpl.read(PlainSocketImpl.java:564)
    at org.apache.harmony.luni.net.SocketInputStream.read(SocketInputStream.java:88)
    at org.apache.http.impl.io.AbstractSessionInputBuffer.fillBuffer(AbstractSessionInputBuffer.java:103)
    at org.apache.http.impl.io.AbstractSessionInputBuffer.readLine(AbstractSessionInputBuffer.java:191)
    at org.apache.http.impl.conn.DefaultResponseParser.parseHead(DefaultResponseParser.java:82)
    at org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:174)
    at org.apache.http.impl.AbstractHttpClientConnection.receiveResponseHeader(AbstractHttpClientConnection.java:179)
    at org.apache.http.impl.conn.DefaultClientConnection.receiveResponseHeader(DefaultClientConnection.java:235)
    at org.apache.http.impl.conn.AbstractClientConnAdapter.receiveResponseHeader(AbstractClientConnAdapter.java:259)
    at org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:279)
    at org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:121)
    at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:410)
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
    at com.PowerHomeConnectorForAndroid.Network$GetHttpData.doInBackground(Network.java:215)
    at com.PowerHomeConnectorForAndroid.Network$GetHttpData.doInBackground(Network.java:1)
    at android.os.AsyncTask$2.call(AsyncTask.java:185)
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
    at java.util.concurrent.FutureTask.run(FutureTask.java:137)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
    at java.lang.Thread.run(Thread.java:1096)

Remember, the problem here is I am trapping the exception, but the code still works, I can see the server receives the command, and I even get a response back from the server.

I did some wireshark sniffing, and a good session and bad session look almost identical, with the exception being the amount of time it takes for the final response to get back to the phone. Since the exception is actually a SocketTimeoutException, I suppose this makes sense, but the reality is that the response does make it back and the phone accepts it as part of the same session, so what is really happening? Was there an exception or not?

Here's the wireshark capture (sorry for the left-right scrolling) The first capture is the bad session and the second one is the good session.

      IOException                                                                                                                                                           x     Good                              
1     http-alt     0             70.165.69.220     192.168.1.110     TCP     66     20180 > http-alt [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1                 x     31     http-alt     0            70.165.69.220     192.168.1.110     TCP     66     52220 > http-alt [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1
2     20180        0.000039      192.168.1.110     70.165.69.220     TCP     66     http-alt > 20180 [SYN, ACK] Seq=0 Ack=1 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1      x     32     52220        0.000043     192.168.1.110     70.165.69.220     TCP     66     http-alt > 52220 [SYN, ACK] Seq=0 Ack=1 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1
3     http-alt     0.05784       70.165.69.220     192.168.1.110     TCP     60     20180 > http-alt [ACK] Seq=1 Ack=1 Win=65536 Len=0                                      x     33     http-alt     0.22131      70.165.69.220     192.168.1.110     TCP     60     52220 > http-alt [ACK] Seq=1 Ack=1 Win=65536 Len=0
4     http-alt     0.153949      70.165.69.220     192.168.1.110     HTTP   196     GET /ph-cgi/clogin HTTP/1.1                                                             x     34     http-alt     0.350917     70.165.69.220     192.168.1.110     HTTP   196     GET /ph-cgi/clogin HTTP/1.1 
5     20180        0.161902      192.168.1.110     70.165.69.220     HTTP  2967     HTTP/1.0 200 OK  (text/html)                                                            x     35     52220        0.3841       192.168.1.110     70.165.69.220     HTTP  2967     HTTP/1.0 200 OK  (text/html)
6     20180        0.161992      192.168.1.110     70.165.69.220     TCP     54     http-alt > 20180 [FIN, ACK] Seq=2914 Ack=143 Win=65536 Len=0                            x     36     52220        0.38419      192.168.1.110     70.165.69.220     TCP     54     http-alt > 52220 [FIN, ACK] Seq=2914 Ack=143 Win=65536 Len=0
7     http-alt     0.209671      70.165.69.220     192.168.1.110     TCP     60     20180 > http-alt [ACK] Seq=143 Ack=1461 Win=65536 Len=0                                 x     37     http-alt     0.614323     70.165.69.220     192.168.1.110     TCP     60     52220 > http-alt [ACK] Seq=143 Ack=1461 Win=65536 Len=0
8     http-alt     0.253024      70.165.69.220     192.168.1.110     TCP     60     20180 > http-alt [ACK] Seq=143 Ack=2915 Win=64000 Len=0                                 x     38     http-alt     0.614456     70.165.69.220     192.168.1.110     TCP     60     52220 > http-alt [ACK] Seq=143 Ack=2915 Win=64000 Len=0
9     http-alt     0.373148      70.165.69.220     192.168.1.110     TCP     60     20180 > http-alt [FIN, ACK] Seq=143 Ack=2915 Win=64000 Len=0                            x     39     http-alt     0.746923     70.165.69.220     192.168.1.110     TCP     60     52220 > http-alt [FIN, ACK] Seq=143 Ack=2915 Win=64000 Len=0
10    20180        0.373172      192.168.1.110     70.165.69.220     TCP     54     http-alt > 20180 [ACK] Seq=2915 Ack=144 Win=65536 Len=0                                 x     40     52220        0.746944     192.168.1.110     70.165.69.220     TCP     54     http-alt > 52220 [ACK] Seq=2915 Ack=144 Win=65536 Len=0
11    http-alt     0.38402       70.165.69.220     192.168.1.110     TCP     66     53091 > http-alt [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1                 x     41     http-alt     0.762482     70.165.69.220     192.168.1.110     TCP     66     64314 > http-alt [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1
12    53091        0.384069      192.168.1.110     70.165.69.220     TCP     66     http-alt > 53091 [SYN, ACK] Seq=0 Ack=1 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1      x     42     64314        0.762517     192.168.1.110     70.165.69.220     TCP     66     http-alt > 64314 [SYN, ACK] Seq=0 Ack=1 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1
13    http-alt     0.425956      70.165.69.220     192.168.1.110     TCP     60     53091 > http-alt [ACK] Seq=1 Ack=1 Win=65536 Len=0                                      x     43     http-alt     1.015043     70.165.69.220     192.168.1.110     TCP     60     64314 > http-alt [ACK] Seq=1 Ack=1 Win=65536 Len=0
14    http-alt     0.511349      70.165.69.220     192.168.1.110     TCP    349     [TCP segment of a reassembled PDU]                                                      x     44     http-alt     1.064351     70.165.69.220     192.168.1.110     TCP    349     [TCP segment of a reassembled PDU]
15    53091        0.704456      192.168.1.110     70.165.69.220     TCP     54     http-alt > 53091 [ACK] Seq=1 Ack=296 Win=65536 Len=0                                    x     45     64314        1.263922     192.168.1.110     70.165.69.220     TCP     54     http-alt > 64314 [ACK] Seq=1 Ack=296 Win=65536 Len=0
16    http-alt     2.562688      70.165.69.220     192.168.1.110     HTTP    99     POST /ph-cgi/cauth HTTP/1.1  (application/x-www-form-urlencoded)                        x     46     http-alt     3.088689     70.165.69.220     192.168.1.110     HTTP    99     POST /ph-cgi/cauth HTTP/1.1  (application/x-www-form-urlencoded)
17    53091        2.567888      192.168.1.110     70.165.69.220     HTTP   355     HTTP/1.0 200 OK  (text/html)                                                            x     47     64314        3.093318     192.168.1.110     70.165.69.220     HTTP   355     HTTP/1.0 200 OK  (text/html)
18    53091        2.568447      192.168.1.110     70.165.69.220     TCP     54     http-alt > 53091 [FIN, ACK] Seq=302 Ack=341 Win=65536 Len=0                             x     48     64314        3.093858     192.168.1.110     70.165.69.220     TCP     54     http-alt > 64314 [FIN, ACK] Seq=302 Ack=341 Win=65536 Len=0
19    http-alt     2.612071      70.165.69.220     192.168.1.110     TCP     60     53091 > http-alt [ACK] Seq=341 Ack=303 Win=65280 Len=0                                  x     49     http-alt     3.313276     70.165.69.220     192.168.1.110     TCP     60     64314 > http-alt [ACK] Seq=341 Ack=303 Win=65280 Len=0
20    http-alt     2.665338      70.165.69.220     192.168.1.110     TCP     66     34654 > http-alt [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1                 x     50     http-alt     3.410808     70.165.69.220     192.168.1.110     TCP     66     33703 > http-alt [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1
21    34654        2.665385      192.168.1.110     70.165.69.220     TCP     66     http-alt > 34654 [SYN, ACK] Seq=0 Ack=1 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1      x     51     33703        3.410851     192.168.1.110     70.165.69.220     TCP     66     http-alt > 33703 [SYN, ACK] Seq=0 Ack=1 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1
22    http-alt     2.665487      70.165.69.220     192.168.1.110     TCP     60     53091 > http-alt [FIN, ACK] Seq=341 Ack=303 Win=65280 Len=0                             x     52     http-alt     3.41086      70.165.69.220     192.168.1.110     TCP     60     64314 > http-alt [FIN, ACK] Seq=341 Ack=303 Win=65280 Len=0
23    53091        2.6655        192.168.1.110     70.165.69.220     TCP     54     http-alt > 53091 [ACK] Seq=303 Ack=342 Win=65536 Len=0                                  x     53     64314        3.41087      192.168.1.110     70.165.69.220     TCP     54     http-alt > 64314 [ACK] Seq=303 Ack=342 Win=65536 Len=0
24    http-alt     2.709857      70.165.69.220     192.168.1.110     TCP     60     34654 > http-alt [ACK] Seq=1 Ack=1 Win=65536 Len=0                                      x     54     http-alt     3.715974     70.165.69.220     192.168.1.110     TCP     60     33703 > http-alt [ACK] Seq=1 Ack=1 Win=65536 Len=0
25    http-alt     2.916243      70.165.69.220     192.168.1.110     HTTP   308     GET /ph-cgi/eval?formula=ph_macro%28%27TESTING%27%29 HTTP/1.1                           x     55     http-alt     3.830971     70.165.69.220     192.168.1.110     HTTP   308     GET /ph-cgi/eval?formula=ph_macro%28%27TESTING%27%29 HTTP/1.1 
26    34654        3.114457      192.168.1.110     70.165.69.220     TCP     54     http-alt > 34654 [ACK] Seq=1 Ack=255 Win=65536 Len=0                                    x     56     33703        3.858623     192.168.1.110     70.165.69.220     HTTP   153     HTTP/1.0 200 OK  (text/html)
27    http-alt     11.023287     70.165.69.220     192.168.1.110     TCP     60     34654 > http-alt [FIN, ACK] Seq=255 Ack=1 Win=65536 Len=0                               x     57     33703        3.858729     192.168.1.110     70.165.69.220     TCP     54     http-alt > 33703 [FIN, ACK] Seq=100 Ack=255 Win=65536 Len=0
28    34654        11.023305     192.168.1.110     70.165.69.220     TCP     54     http-alt > 34654 [ACK] Seq=1 Ack=256 Win=65536 Len=0                                    x     58     http-alt     4.114668     70.165.69.220     192.168.1.110     TCP     60     33703 > http-alt [ACK] Seq=255 Ack=101 Win=65536 Len=0
29    34654        34.882577     192.168.1.110     70.165.69.220     TCP     54     http-alt > 34654 [FIN, ACK] Seq=1 Ack=256 Win=65536 Len=0                               x     59     http-alt     4.153392     70.165.69.220     192.168.1.110     TCP     60     33703 > http-alt [FIN, ACK] Seq=255 Ack=101 Win=65536 Len=0
30    http-alt     34.926041     70.165.69.220     192.168.1.110     TCP     60     34654 > http-alt [ACK] Seq=256 Ack=2 Win=65536 Len=0                                    x     60     33703        4.153402     192.168.1.110     70.165.69.220     TCP     54     http-alt > 33703 [ACK] Seq=101 Ack=256 Win=65536 Len=0

So, perhaps I should just ignore a SocketTimeoutException??? Sounds kind of dangerous....

Since the error happens at that execute.getEntity() line, I didn't think it was necessary to have the code after that point. Anyway, thanks for the help offer. The rest of the code has been added. I hope it helps! :) — MrGibbage
– MrGibbage, Commented Feb 9, 2012 at 13:42
Where did everyone go? I have still been looking into this and I can't figure out what I should change to make this error not show up. Perhaps I'm doing it wrong? — MrGibbage
– MrGibbage, Commented Feb 12, 2012 at 3:11
Well, I am going to leave this open in the hopes that someone will come by and see it and have a good answer. In the meantime, I have disabled the reporting of this error in my app. Perhaps I have found an android bug??? — MrGibbage
– MrGibbage, Commented Feb 12, 2012 at 20:29

Mandar Pandit · Accepted Answer · 2015-01-12 07:41:57Z

I think the problem is in the socket time out you have in this line :

HttpConnectionParams.setSoTimeout(httpParams, 5000);

If we look to this part of the HttpClient Documentation: http://hc.apache.org/httpclient-legacy/exception-handling.html

For instance, the HTTP server will consider its part of the contract fulfilled if it succeeds in receiving and processing the request, generating a response and sending a status code back to the client. The server will make no attempts to roll back the transaction if the client fails to receive the response in its entirety due to a read timeout, a request cancellation or a system crash. If the client decides to retry the same request, the server will inevitably end up executing the same transaction more than once. In some cases this may lead to application data corruption or inconsistent application state.

The fact that the server is receiving the request and sending a response could be what the documentation is describing. The solution would be to increase the SoTimeout or retry your request:

HttpRequestRetryHandler retryHandler = new HttpRequestRetryHandler(){
        @Override
        public boolean retryRequest(IOException exception,
                int executionCount, HttpContext context) {

            if (executionCount >= 5) {
                Log.e("Retry Limit", "Retry #: " + executionCount);
                return false;
            }

            if(exception instanceof java.net.SocketTimeoutException){
                Log.e("(SocketTimeoutException)", "Retry #: " + executionCount);
                return true;
            }
            if(exception instanceof java.net.SocketException){
                Log.e("(SocketException)", "Retry #: " + executionCount);
                return true;
            }
            if(exception instanceof ObjectStreamException){
                Log.e("(ObjectStreamException)", "Retry #: " + executionCount);
                return true;
            }
            if(exception instanceof ProtocolException){
                Log.e("(ProtocolException)", "Retry #: " + executionCount);
                return true;
            }
            if(exception instanceof SSLException){
                Log.e("(SSLException)", "Retry #: " + executionCount);
                return true;
            }
            if(exception instanceof SyncFailedException){
                Log.e("(SyncFailedException)", "Retry #: " + executionCount);
                return true;
            }
            if(exception instanceof UTFDataFormatException){
                Log.e("(UTFDataFormatException)", "Retry #: " + executionCount);
                return true;
            }
            return false;
        }
    };
    client.setHttpRequestRetryHandler(retryHandler);

This will catch the SocketTimeOut,SocketException etc. But if you get a IOException you could retry the request manually:

catch (IOException e)
{
    SystemClock.sleep(1500);
       Log.e(MY_ERROR_TAG, "IOException: " + e.getMessage());
     Toast.ShowToast("Error connecting to server.", pa);
    /*RETRY THE REQUEST MANUALLY*/
}

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