can you please let me know the process happening during 4903,4904,4905,4906 and 4907
wireshark file
During 4903 the data is lost and during 4909 the actual data i am getting at 4913 also same date is received during 4914
Related
I will implement the data exchange between the module and the device Sim5360e through UART2. I write in the Lua, AT commands to send / receive information via the UART2 did not find - so use internal devio function.
sio.send("AT+CSCLK=0\r\n")
readAndPrintAtUnswer()
sio.send("AT+CGFUNC=21,1\r\n")
readAndPrintAtUnswer()
sio.send("AT+IPR2=9600\r\n")
readAndPrintAtUnswer()
local msg,count=getHex(str)
local unswer
devio.open(3)
devio.write(3,msg,count)
unswer=devio.read(3,4000)
print(unswer)
devio.close(3)
When connected to a terminal on the PC - see the correct incoming message, the module enters the mode of reading, I send data through the terminal, but after a timeout (4000 ms) unswer = nil. Data from the terminal out exactly correct - checked by another device.
Can you please tell, how do I get an answer to my message?
things are like this:
I used AsyncSocket to connect with server. when the server send some bytes to client at a time, app will invoke (onSocket: didReadData: withTag:) method; Sometimes, because of the network or other reason, some bytes arrived and the rest bytes arrived later( which means some bytes are delayed).(timeOut = -1)
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Question: how much times did the method(onSocket: didReadData: withTag: ) invoke?
1)only one time - it will wait automatically until the bytes are complete？
2)2 or more times - some arrived(invoke), other arrived(invoke)、、、、、like so?
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which thoughts is right? plz geiv me some advice. Thanks very much.
OK， maybe it's just like this.
Transfer data on TCP: when you send 1000 bytes at a time, because of lag or other reasons, you may receive the 900 bytes first, but the TCP socket will wait the rest 100 bytes
automatically. So if I use asyncSocket to transfer datas and set the timeout, during these seconds, I don't need to deal with the lagged data.
=========================
EDIT
maybe the title of ths question is not appropriate, no one cares the question.
I used the method -readDataToLength: instead, first read header.length of data, and parse it, then read the body.length of data;
I have a device that sends data to my server via gprs . The problem is that it sends raw data and i don't know where i can stop the reading
Currently i am using something TIdHttpServer and something like this to read the strings :
var
s : string;
repeat
s:=s+acontext.Connection.Socket.ReadChar;
until acontext.Connection.Socket.InputBufferIsEmpty;
Is there a better solution to my problem ?
TCP is stream oriented. If the protocol is unknown, the server only can try to read into a byte array (if memory is not a problem) or a file stream. If the client disconnects normally, the data is 'complete'. Unfortunately, if the protocol is unknown, the server can not tell wether the client died or disconnected normally.
InputBufferIsEmpty does not help, as it only says if there is data in the (TCP) buffer - and depending on latency this can happen frequently, but it does not mean that there are no more in-flight bytes.
You could try to 'reverse engineer' the protocol, by sending known strings over the client devices. But if the sender is a black box, there can be many special cases - think of encoding or 'escape' characters etc.
You could make up you own protocol.
Some ideas are:
use a special character or characters combo to define the end of the
message.
append at the start of the message some fixed size field with the size of the message
I'm new to delphi and this is my first project.
Here's a little bit of code:
procedure TForm1.Button2Click(Sender: TObject);
responseStringFromServer:TStringStream;
begin
try
if IdTCPClient1.Connected then
begin
dataSentToDevice:= 'http/1.0 content-length: 344 content-type: text/xml <?xml version="1.0" encoding="UTF-8" ?> ...'
IdTCPClient1.IOHandler.WriteLn(dataSentToDevice);
responseStringFromServer := TStringStream.Create;
IdTCPClient1.IOHandler.ReadStream(responseStringFromServer);
...
I have a device connected to local network. I manage to connect to it succesfully. Sending commands is working too, but when i do
IdTCPClient1.IOHandler.ReadStream(responseStringFromServer);
then it waits til device is done processing and an exception occurs: "Connection Closed Gracefully". So i'm not able to read data the device is supposed to send me. Device is not shutting down. I've read other posts and i understand that device itself drops connection.
I have a demo program that communicates with it and it works fine. I need to get response xml before it drops the connection.
Also the request is http and i am using IdTCPClient (i need to use xml request, i don't know how to do it with TidHTTP).
May it be that after device is sending response it drops the connection, so that my tcpclient gets connection dropped flag before receiving data.
Any help would be appreciated!
Also the request is http and i am
using IdTCPClient (i need to use xml
request, i don't know how to do it
with TidHTTP).
Working with IdHTTP is simple...
Drop an instance of it on your form,
select it.
In Object Inspector, go to
ProtocolVersion property, and set it
to pv1_0, then open its
Request property set, and set
Request.ContentType to text/xml, and
Request.ContentEncoding to UTF-8,
and set other properties if
required.
Add a button to your form and
double-click on it.
In your code, create an instance of
TStringStream, and load your XML
content into it.
Assign your stream to
IdHttp.Request.Source.
Call IdHttp.Get() method by giving
it a host address.
IdHttp.Get() returns a string which
is the response the server sent you.
The way you are calling ReadStream(), it will interpret the first 4 bytes (or 8 bytes if the TIdIOHandler.LargeStream property is True) as an Integer (or Int64) in network-byte order that specifies the length of the data, and then it will try to read that many bytes. Is the device actually sending such a length value? If not, then ReadStream() will attempt to read the wrong number of bytes. An EIdConnClosedGracefully exception means the device is closing the socket on its end. So either the device is closing the connection immediately after sending its data, or it is timing out waiting for you to send the next command, which you cannot do since you are blocked waiting for the wrong data from the previous command.
As said by #Remy Lebeau and the documentation (press F1 when your edit caret is over the ReadStream sentence):
AByteCount indicates the number of bytes from the IOHandler to be read into AStream. When AByteCount contains -1 and AReadUntilDisconnect contains False, the byte count is read as an Integer value from the IOHandler. The size of AStream is adjusted to match the size expected from the IOHandler.
This is very useful when you're connecting to servers written also in INDY WriteStream in one end, ReadStream in the other, or any other language if you send that byte cound as expected by INDY client.
If you're reading from a device, be sure the device is sending that info up-front the stream or change the way you read the data. If you know the size of the stream, just pass the second parameter: AByteCount. If the device will close the channel when the stream ends, pass -1 as the second parameter and True as the third parameter: AReadUntilDisconnect.
If the device send text of unknown length but using a known terminator (like CR/LF), you better use ReadLn method of IOHandler to get that string.
Take a look at if neither fits your needs, take a look on Read* methods of TIOHandlerClass and RTFM for each to find the correct one to get the data sent by the device.
I am sending data to the server twice. First, I send "Hello world" and then I send "Server".
But the server received the data at 1 read. But the server have to read the data in a two-read operation.
Also, I write the data. Then read data from server and then I write the data.
In this case, the server can read the first data. But server can not read the second data.
The server uses read, write, read.
So how to overcome this issue? How do I write data to socket in BlackBerry?
What you describe is how TCP is supposed to work by default. What you are seeing is the Nagle algorithm (RFC 896) at work, reducing the number of outbound packets being sent so they are processed as efficiently as possible. You may be sending 2 packets in your code, but they are being transmitted together as 1 packet. Since TCP is a byte stream, the receiver should not be making any assumptions about how many packets it gets. You have to delimit your packet data in a higher-level protocol, and the receiver has to process data according to that protocol. It has to handle cases where multiple packets arrive in a single read, a single pakcet arriving in multiple reads, and everything in between, only processing packet data when they have been received in full, caching whatever is left over for subsequent reads to process when needed.
Hard to say without a little more detail, but it sounds like you're using 1-directional communication in the first case - i.e. the client writes, then writes again. There are any number of reasons that the server would receive the 2 writes as 1 read. Buffering on the client, somewhere in the wireless stack (or in the BES), buffering on the server side. All of those are legal with TCP/IP.
Without knowing anything more about your solution, have you thought about defining a small protocol - i.e. the client writes a known byte or bytes (like a 0 byte?) before sending the second write? Then the server can read, then recognize the delimiting byte, and say 'aha, this is now a different write from the client'?
As previously said this is an expected TCP behavior to save bandwidth. Note that to deliver your package TCP adds lot of data (e.g. destination port,sequence number, checksums...).
Instead of flushing the data I´ll recommend you to put more work in your protocol. For example you can define a header that contains the number of bytes to read and then the payload (the actual data).
The following code is a protocol encoded in an string with the structure [length];[data]
StringBuffer headerStr = new StringBuffer();
StringBuffer data = new StringBuffer();
//read header
char headerByte = dataInputStream.readChar();
while (headerByte != ';') {
headerStr.append(headerByte);
headerByte = dataInputStream.readChar();
}
//header has the number of character to read
int header= Integer.parseInt(headerStr.toString());
int bytesReaded = 1;
char dataByte = dataInputStream.readChar();
//we should read the number of characters indicated in the header
while (bytesReaded < header) {
data.append(dataByte);
dataByte = dataInputStream.readChar();
bytesReaded++;
}
For the first query, I guess you are using TCP. If you use UDP, then the server will read the packets in the order you want.
Can you be more clear/elaborative on the second query ?
I would try explicitly telling Connector.open to open up the stream as read_write. Then I would ensure that I flush my connections after each time I talked to the server.
SocketConnection connection = (SocketConnection) Connector.open(url, Connector.READ_WRITE);
OutputStream out = connection.openOutputStream();
// ... write to server
out.flush()
I got a solution to overcome to extract both the string
On sender device
Create a header which contains details of that data eg the data
length, datatype etc.
Add this header to the actual data and send it
On recipient device
read the header
retrieve the actual data length from the header
read the next data upto the data length as specified by the header