On 05.09.2016 15:09, Klemens Muthmann wrote:
Am 05.09.2016 um 14:49 schrieb Tim Watts:
On Mon, 2016-09-05 at 14:11 +0200, Klemens Muthmann wrote:
Hi,
I currently need to implement an HTTP data transmission from an Arduino
with WiFi module to a PC running a Tomcat 8.5.4 instance. The Tomcat is
running under Ubuntu 16.04.
The problem is that, since there are no HTTP libraries on Arduino, I
need to write the correct HTTP request myself and I got stuck. It would
be great if someone on the list with a deeper understanding of the HTTP
protocol would be willing to support me.
The transmitted (possibly erroneous ) request looks like:
========================================
GET /push?VIN=testrun HTTP/1.1
User-Agent: Freematics
Connection: keep-alive
Host:
========================================
The server runs under a local access point IP (10.42.0.1) and receives
that request correctly but throws me an EOFException from the following
code fragment:
nRead = channel.read(socketBufferHandler.getReadBuffer());
if (nRead == -1) {
throw new EOFException();
}
So it seems to me that an end of file is reached before it is expected.
Can somebody provide me with hints on how to solve that issue and
formulate a correct HTTP request to my Tomcat instance?
The following is th log trace I receive from the server:
========================================
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
o.a.coyote.http11.Http11InputBuffer : Received [GET
/push?VIN=testrun HTTP/1.1
User-Agent: Freematics
Connection: keep-alive
Host:
]
Until a real expert comes along with a better answer let me just toss
this out: Are the lines in the HTTP request that the Arduino submits
terminated with \r\n (and not just \n)? Because it looks like the
entire request may have been read when reading the request line. Then
when it goes to read the headers it gets an EOF. Not 100% sure of this
but it's possible.
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
o.a.c.authenticator.AuthenticatorBase : Security checking request GET
/push
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
org.apache.catalina.realm.RealmBase : No applicable constraints
defined
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
o.a.c.authenticator.AuthenticatorBase : Not subject to any constraint
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
org.apache.tomcat.util.http.Parameters : Set encoding to UTF-8
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
org.apache.tomcat.util.http.Parameters : Decoding query null UTF-8
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
org.apache.tomcat.util.http.Parameters : Start processing with input
[VIN=testrun]
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
o.s.b.w.f.OrderedRequestContextFilter : Bound request context to
thread: org.apache.catalina.connector.RequestFacade@75c83bc4
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
o.s.web.servlet.DispatcherServlet : DispatcherServlet with name
'dispatcherServlet' processing GET request for [/push]
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
s.w.s.m.m.a.RequestMappingHandlerMapping : Looking up handler method for
path /push
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
s.w.s.m.m.a.RequestMappingHandlerMapping : Returning handler method
[public void de.cyface.obd2.controller.Obd2Controller.push()]
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
o.s.b.f.s.DefaultListableBeanFactory : Returning cached instance of
singleton bean 'obd2Controller'
2016-09-05 13:32:50.238 DEBUG 13143 --- [nio-8080-exec-1]
o.s.web.servlet.DispatcherServlet : Last-Modified value for
[/push] is: -1
push
2016-09-05 13:32:50.239 DEBUG 13143 --- [nio-8080-exec-1]
o.s.web.servlet.DispatcherServlet : Null ModelAndView returned to
DispatcherServlet with name 'dispatcherServlet': assuming HandlerAdapter
completed request handling
2016-09-05 13:32:50.239 DEBUG 13143 --- [nio-8080-exec-1]
o.s.web.servlet.DispatcherServlet : Successfully completed request
2016-09-05 13:32:50.239 DEBUG 13143 --- [nio-8080-exec-1]
o.s.b.w.f.OrderedRequestContextFilter : Cleared thread-bound request
context: org.apache.catalina.connector.RequestFacade@75c83bc4
2016-09-05 13:32:50.239 DEBUG 13143 --- [nio-8080-exec-1]
o.apache.coyote.http11.Http11Processor : Socket:
[org.apache.tomcat.util.net.NioEndpoint$NioSocketWrapper@2940dec1:org.apache.tomcat.util.net.NioChannel@34a92297:java.nio.channels.SocketChannel[connected
local=/10.42.0.1:8080 remote=/10.42.0.72:46701]], Status in:
[OPEN_READ], State out: [OPEN]
2016-09-05 13:32:55.280 DEBUG 13143 --- [nio-8080-exec-2]
o.apache.coyote.http11.Http11Processor : Error parsing HTTP request header
java.io.EOFException: null
at
org.apache.tomcat.util.net.NioEndpoint$NioSocketWrapper.fillReadBuffer(NioEndpoint.java:1222)
~[tomcat-embed-core-8.5.4.jar:8.5.4]
at
org.apache.tomcat.util.net.NioEndpoint$NioSocketWrapper.read(NioEndpoint.java:1163)
~[tomcat-embed-core-8.5.4.jar:8.5.4]
at
org.apache.coyote.http11.Http11InputBuffer.fill(Http11InputBuffer.java:742)
~[tomcat-embed-core-8.5.4.jar:8.5.4]
at
org.apache.coyote.http11.Http11InputBuffer.parseRequestLine(Http11InputBuffer.java:404)
~[tomcat-embed-core-8.5.4.jar:8.5.4]
at
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:994)
~[tomcat-embed-core-8.5.4.jar:8.5.4]
at
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
[tomcat-embed-core-8.5.4.jar:8.5.4]
at
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:785)
[tomcat-embed-core-8.5.4.jar:8.5.4]
at
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1425)
[tomcat-embed-core-8.5.4.jar:8.5.4]
at
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
[tomcat-embed-core-8.5.4.jar:8.5.4]
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
[na:1.8.0_91]
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
[na:1.8.0_91]
at
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
[tomcat-embed-core-8.5.4.jar:8.5.4]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_91]
=======================================
Thanks and regards
Klemens
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Hi,
Thanks for the answer.
The request is formatted on the Arduino like:
"GET /push?VIN=testrun HTTP/1.1\r\nUser-Agent: Freematics\r\nConnection:
keep-alive\r\nHost: \r\n"
So yes, all lines are terminated with \r\n
and are you sure that the software that you use on the Arduino really replaces "\r\n" by a
real CR/LF pair before sending this to the server ?
(If you set up an Access log on Tomcat, you can check this).
(aside : there is nothing "magical" in the string "\r\n" at the level of the HTTP
protocol. For HTTP, these are just 4 normal printable characters. The possible "\r\n"
replacement by a CR/LF pair is a function of what you use *on the agent* to interpret that
string before printing it.)
Also, it seems to me that since you are specifying "HTTP/1.1" as the protocol in our
request, the "Host:" line should include a host name. If your Tomcat only has a default
Host entry, then use whatever you feel like (Tomcat will default to that default Host anyway).
If your Tomcat has several <Host> entries, use the appropriate hostname.
Like :
Host: mytomcat.mycompany.com<CR/LF>
You /may/ also want to add a header :
Content-length: 0<CR/LF>
although in principle that should not be necessary, since a GET request normally has no
request body.
Maybe try the following, as a confirmation :
- get an appropriate add-on to a normal browser, which shows the trace of the conversation
with the server. Examples :
- for IE : Fiddler2
- for Mozilla : HttpFox, LiveHttpHeaders or similar
- then activate it,
then issue the same request from the browser to your Tomcat, and look at the HTTP
conversation in the add-on window.
To send the same request as above, type this in the browser's URL bar :
http://mytomcat.mycompany.com//push?VIN=testrun
(the default request is GET)
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