I have a question, I would like to know whether ConectionRequest returns response code is 502 or 0 when internet connection lost during the query on Mobile device. Testing Tool returns 502 when there is no internet and debugging the code in Simulator returns response code 0. I would like to know what would be the response code when there is no connectivity during network call. Please advise.
Also, is there a better method to detect offline mode during the network call. I'm aware of Connectivity lib already.
Thanks
This will behave in an inconsistent way because the underlying platforms behave very differently. You need to test for positive responses e.g. server returned 200 instead of testing for negative outcome such as error codes.
You should get an error response callback but we can't guarantee it.
Related
I'm trying to make a forwarding proxy but I keep getting an
Alert(Level: Fatal, Description: Decode Error)
after the Client sends...
Client Key Exchange, Change Cipher Spec, Encrypted Handshake Message
Any ideas as to what I'm doing wrong?
I can't seem to get a grasp on what the error even means. Does it mean
the initial encrypted packet by the client fails to be decrypted by
the server? If so, then why?
UPDATE 1
I just was looking at the packets and I noticed a significant difference between using my proxy, and not using the proxy.
The DFE key isn't being interpereted with my proxy.
Any ideas as to what I'm doing wrong?
You're not forwarding the exact amount of data that the proxy is supposed to forward.
But I see you're going further now than at the beginning of your question (good !)
You are implementing a proxy which forwards every single byte which it receives, in both ways, and either it sends too much to the server, or not enough. Check your code again for any conditions when you stop reading the input data to forward, be sure you're forwarding exactly everything. Nothing more, nothing less.
RFC 5246, about Decode Error :
decode_error
A message could not be decoded because some field was out of the
specified range or the length of the message was incorrect. This
message is always fatal and should never be observed in
communication between proper implementations (except when messages
were corrupted in the network).
Actually I'm using D-Feet (D-Feet can be used to inspect D-Bus interfaces of running programs and invoke methods on those interfaces) to connect to a BLE peripheral that advertises proximity profile.
When I try the Connect() method on the remote object /org/bluez/hci0/dev_88_6B_0F_00_C4_3A every thing is fine and the connection succeed but when I try to connect only the proximity profile using ConnectProfile("0x1802") method an error occurs saying that the host is down:
g-io-error-quark: GDBus.Error:org.bluez.Error.Failed: Host is down
(36)
Can anyone help me solving this problem (I'm blocked for 2 weeks and there still to much to deal with in the project :/)
ConnectProfile("0x1802")
ConnectProfile (and the Bluez API in general) does not deal with handles, only UUIDs. Your input argument does not look like a UUID: I suggest you find the remote service UUID that matches the handle (I'm assuming your current input argument is a handle).
I believe you can find the UUID with d-feet (after Connect() the service objects should be there) or with bluez command line tools.
I'm currently working on a C application sending message to a Meteor server over websocket.
I'm using jansson for JSON conversion and nopoll as websocket library.
Everything is working fine in both way (sending / receiving) except when I try to send very large messages (about 15 000 000 characters). I think (I'm not sure) that the message is sent to the server so the nopoll library should not be the source of the issue. But, I'm sure that the message is not treated by Meteor as he should be, because the method (RPC) is never called.
I found that the websocket limitation is equal to the maximum value of a 64-bit unsigned value so this shouldn't be the problem.
On the other hand, I didn't found the maximum length for a DDP message even in the DDP specification.
Have you any idea of the DDP limitation or other parameters that I didn't think about ?
As I was working on an architecture where the client and the server was on the same machine, I was not limited by the network. I think I was pushing too much informations too fast, and the socket was simply full of data.
The solution is simple : cut the data in several fragments as LPs suggests and implement flow-control.
I also found the Mongo C driver that could be another solution because I should be able to push data directly on the database as suggests Mikkel.
Thank you both for your help.
We recently developed an application which will run a query in DB2 and send a mail to the corresponding recipient. It works well in our local system and QA region. But in production, few queries failed (even if it's rare, like once in week). It throws the exception below.
Exception InnerDetails:
ERROR [40003] [IBM][CLI Driver] SQL30081N A communication error has
been detected. Communication protocol being used: "TCP/IP".
Communication API being used: "SOCKETS". Location where the error was
detected: "111.111.111.111". Communication function detecting the
error: "recv". Protocol specific error code(s): "10004", "", "".
SQLSTATE=08001
Since error occurs only in production and not very often, we are not sure whether it is the code or a setting issue. Do you have any idea?
We recently discussed this issue with our IBM rep. After looking in their internal knowledge base, he suggested we add "Interrupt=0" to our connection string, based on recommendations given to other customers that had the same problem.
The default value for Interrupt was 1 before v10.5 FP2 and still is for most connections. They changed the default value to 2 for connections to z/OS (mainframe) in FP2.
We're using C# and the connection string properties for the IBM Data Server Driver for .Net can be found here. I'm sure there is a similar property for their drivers for other languages.
This page from the IBM docs goes into a bit more detail about the setting.
We haven't seen the issue since we recently added the property, but it was always intermittent so I can't yet confidently say that the problem is fixed. Time will tell...
That particular error (SQL30081N) is just a generic message that indicates a network issue between your DB2 client and the server. In this case, you want to look at the Protocol specific error code(s). Here, it looks like you're on Windows, and that particular code (10004) isn't given in the IBM documentation.
So, if you google "windows network error codes", you'll find this page, which says:
WSAEINTR
10004
Interrupted function call.
A blocking operation was interrupted by a call to WSACancelBlockingCall.
Which links to this page with more information on that specific function (emphasis mine):
The WSACancelBlockingCall function has been removed in compliance
with the Windows Sockets 2 specification, revision 2.2.0.
The function is not exported directly by WS2_32.DLL and Windows
Sockets 2 applications should not use this function. Windows Sockets
1.1 applications that call this function are still supported through the WINSOCK.DLL and WSOCK32.DLL.
Blocking hooks are generally used to keep a single-threaded GUI
application responsive during calls to blocking functions. Instead of
using blocking hooks, an applications should use a separate thread
(separate from the main GUI thread) for network activity.
I'm guessing that your application may be blocking for a longer time in your production application than your other environments, and something along the way is causing the interrupt.
Hopefully this leads you down the right path...
I spent hours to solve the same problem and fixed it. I use a Windows exe (developed with C#.NET) to run a SELECT query from a DB2 database and I sometimes got this error. Finally I realized that my problem is a time out error. Error with protocol code "10004" message, sometimes occurs if query execution is longer than 30 seconds which is default timeout value. Maybe the interruption call on the "Windows Socket Error Codes" page occurs for time out mechanism. I add aline to set an acceptable timeout value and got rid off this annoying error. I hope it helps other.
Here is my code fix :
...
connDb.Open();
DB2Command cmdDb = new DB2Command(QueryText,connDb);
cmdDb.CommandTimeout = 300; //I added this line.
using (DB2DataReader readerDb = cmdDb.ExecuteReader())
{
...
I'm attempting to write my own http 1.1 server, just for fun and learning about more about HTTP, sockets, and threading.
I've gotten a good start i think with only delivering static pages (using c, which I would prefer to stay in for the time being). I have a test page I wrote a while ago and deliver it's ~50 files in 124ms according to chrome, without using threads or keep-alive sockets.
I've found it very difficult to get threading/keep-alive working at all. There are little to no resources on the web (that I can find in my hours of Googling) that explain keep-alive connections in detail. If anyone could recommend a good book on HTTP server programming, I would greatly appreciate it.
I've done some threading and socket programming before by making a simple chat program, so I have at least some experience with it.
The issue I'm having is that when I attempt to incorporate threads, the client browser sets up multiple connections. Somewhere along the line, the server gets confused and the client just sits there waiting for responses and the server stops doing anything. I send the Connection: Keep-Alive header, but that doesn't change anything and when I incorporate keep-alive it and create a loop for getting requests in the threaded function, it stalls until the connection is closed.
I would appreciate it if someone could give me some pseudo code on how to get keep alive/threading working for this so the client stops creating multiple connections at a time.
A brief description of whats going on:
main function
load in static pages to large array of fileinfo struct that hold the file data and length
create the socket
set it to listen to port 80
set it to listen for 10 connections at a time(i know this is low...)
start an endless loop
block while waiting for someone to connect
check if it's a localhost connection
shutdown the server
otherwise
start a thread(with pthread), sending it the socket variable
loop
Thread Function
setsock opt for 3 sec timeout on send/recv and enable Keep-alive
start endless loop
read in request
if request timed out, break the loop
Validate Request function call
Create Reponse function call
Send response
if request contained Connection: close header break the loop
loop
close socket
return
I would recommend looking at GNU libmicrohttpd. It focuses squarely on providing a framework upon which to build HTTP 1.1 servers. It is small and supports keep-alive with and without threading. (Personally I use it without threading. It has several threading models too.)
Even if you decide to write your web server from scratch, I would suggest looking at libmicrohttpd to gain insight in not only how the protocol works, but how the library models "the work flow" of a web server in a very clean way. I think it is a mistake to imagine that keep-alive implies threading and I think it is an impediment to understanding keep-alive.
(Regarding Apaches' credits as a web server, it is pretty huge, and there is a lot in there not related to protocols, but rather things like its plugin system and so on.)
I'd recommend grabbing the source for Apache and seeing how they handle it. There's not much point in psuedo code when you can see how the real thing works.
Perhaps you could look at Apache's code for some clues. It is written in C.
Hopefully someone will come along and give a more detailed answer :)