I have created connection with a hard ware device , using CGDAsyncSocket , but now next step is to send binary data to that device , so i am very much confused how to construct that packet whose description is given below
field=packet_id
byte=1
value=0X01
Please help I am weired on this point
usually using CGDAsyncSocket is pretty simple:
NSData *chunkSize = you data, + (id)dataWithBytes:(const void *)bytes length:(NSUInteger)length can be used to setup u own packet.
[asyncSocket writeData:chunkSize withTimeout:TIMEOUT_WRITE_HEAD tag:HTTP_CHUNKED_RESPONSE_HEADER];
here is instruction to construct bytes:
https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/BinaryData/Tasks/WorkingMutableData.html
example:
const unsigned char newBytes[4] = { 0x08, 0x08, 0x08, 0x08 };
Related
I've been creating a virtual ethernet interface. I've opened asynchronous communication with a controlling application and every time there are new packets, the controlling app is notified and then asks for the packet data. The packet data is stored in a simple struct, with uint8_t[1600] for the bytes, and uint32_t for the length. The dext is able to populate this struct with dummy data every time a packet is available, with the dummy data visible on the controlling application. However, I'm struggling to fill it with the real packet data.
The IOUserNetworkPacket provides metadata about a packet. It contains a packets timestamp, size, etc, but it doesn't seem to contain the packet's data. There are the GetDataOffset() and GetMemorySegmentOffset() methods which seem to return byte offsets for where the packet data is located in their memory buffer. My instinct tells me to add this offset to the pointer of wherever the packet data is stored. The problem is I have no idea where the packets are actually stored.
I know they are managed by the IOUserNetworkPacketBufferPool, but I don't think that's where their memory is. There is the CopyMemoryDescriptor() method which gives an IOMemoryDescriptor of its contents. I tried using the descriptor to create an IOMemoryMap, using it to call GetAddress(). The pointers to all the mentioned objects lead to junk data.
I must be approaching this entirely wrong. If anyone knows how to access the packet data, or has any ideas, I would appreciate any help. Thanks.
Code snippet within IOUserClient::ExternalMethod:
case GetPacket:
{
IOUserNetworkPacket *packet =
ivars->m_provider->getPacket();
GetPacket_Output output;
output.packet_size = packet->getDataLength();
IOUserNetworkPacketBufferPool *pool;
packet->GetPacketBufferPool(&pool);
IOMemoryDescriptor *memory = nullptr;
pool->CopyMemoryDescriptor(&memory);
IOMemoryMap *map = nullptr;
memory->CreateMapping(0, 0, 0, 0, 0, &map);
uint64_t address = map->GetAddress()
+ packet->getMemorySegmentOffset();
memcpy(output.packet_data,
(void*)address, packet->getDataLength());
in_arguments->structureOutput = OSData::withBytes(
&output, sizeof(GetPacket_Output));
// free stuff
} break;
The problem was caused by an IOUserNetworkPacketBufferPool bug. My bufferSize was set to 1600 except this value was ignored and replaced with 2048. The IOUserNetworkPackets acted as though the bufferSize was 1600 and so they gave an invalid offset.
Creating the buffer pool and mapping it:
kern_return_t
IMPL(FooDriver, Start)
{
// ...
IOUserNetworkPacketBufferPool::Create(this, "FooBuffer",
32, 32, 2048, &ivars->packet_buffer));
packet_buffer->CopyMemoryDescriptor(ivars->packet_buffer_md);
ivars->packet_md->Map(0, 0, 0, IOVMPageSize,
&ivars->packet_buffer_addr, &ivars->packet_buffer_length));
// ...
}
Getting the packet data:
void FooDriver::getPacketData(
IOUserNetworkPacket *packet,
uint8_t *packet_data,
uint32_t *packet_size
) {
uint8_t packet_head;
uint64_t packet_offset;
packet->GetHeadroom(&packet_head);
packet->GetMemorySegmentOffset(&packet_offset);
uint8_t *buffer = (uint8_t*)(ivars->packet_buffer_addr
+ packet_offset + packet_head);
*packet_size = packet->getDataLength();
memcpy(packet_data, buffer, *packet_size);
}
I am using STM32F103C8T6 board and CubeMX to generate the code. I need to receive the GPS data from Quectel L89 module from UART2 port. when I try that I get some junk values only... I am using HAL_UART_Receive to receive data and print it in the putty console. Any help would be greatly appreciated.
This is my code.
void task1(void)
{
char *buffer = NULL;
buffer = (char*)malloc(400 * sizeof(char));
while(1)
{
HAL_UART_Receive(&huart2,buffer,350,500);
int size = strlen(buffer);
HAL_UART_Transmit(&huart1,buffer,size,500);
HAL_Delay(1000);
}
}
Image of the Result
try this
HAL_UART_Receive(&huart2,(uint8_t *)buffer,350,500);
and
HAL_UART_Transmit(&huart1,(uint8_t *)buffer,size,500);
Because arguments needed for HAL functions are of uint8_t * type.
I am having trouble with my university project for embedded systems. The goal is to establish an interface between a SM5100B GSM module and ATMEGA16A microcontroller, using UART (which I did, using the correct ports from the datasheets), and to be able to send/receive simple SMS messages by sending AT commands trough the Tx and Rx ports from atmega to gsm and vice versa, via C code in Atmel.(not using hyperterminal)
When I tested the GSM module using TeraTerm, i was able to connect properly, and send AT commands easily, also managed to send and recieve an SMS with the SIM card inserted, so everything works fine.
Now I'm trying to do that using the microcontroller.
Here is the code I have so far:
#define F_CPU 7372800UL
#include <stdio.h>
#include <stdlib.h>
#include <util/delay.h>
#include <avr/io.h>
#include <string.h>
#define BAUD 9600
#define MYUBRR ((F_CPU/16/BAUD)-1) //BAUD PRESCALAR (for Asynch. mode)
void GSM_init(unsigned int ubrr ) {
/* Set baud rate */
UBRRH = (unsigned char)(ubrr>>8);
UBRRL = (unsigned char)ubrr;
/* Enable receiver and transmitter */
UCSRB = (1<<RXEN)|(1<<TXEN);
/* Set frame format: 8data, 2stop bit */
UCSRC = (1<<URSEL)|(1<<USBS)|(3<<UCSZ0);
}
void USART_Transmit(char data ) {
/* Wait for empty transmit buffer */
while ( !( UCSRA & (1<<UDRE)) );
/* Put data into buffer, sends the data */
UDR = data;
}
void USART_Transmits(char data[] ) {
int i;
for(i=0; i<strlen(data); i++) {
USART_Transmit(data[i]);
_delay_ms(300);
}
}
int main(void)
{
GSM_init(MYUBRR);
char text_mode[] = "AT+CMGF=1";
char send_sms[] = "AT+CMGS=";
char phone_number[] = "00385*********";
char sms[] = "gsm sadness";
USART_Transmits(text_mode);
_delay_ms(1000);
USART_Transmits(send_sms);
_delay_ms(1000);
USART_Transmit(34);//quotation mark "
//_delay_ms(300);
USART_Transmits(phone_number);
//_delay_ms(300);
USART_Transmit(34);//quotation mark "
//_delay_ms(300);
USART_Transmit(13);//enter
//_delay_ms(300);
USART_Transmits(sms);
_delay_ms(1000);
USART_Transmit(26);//ctrl+z
_delay_ms(300);
USART_Transmit(13);//enter
_delay_ms(3000);
while (1)
{
}
}
However, my code isn't working, it's not sending the message.
The functions for transmitting are taken from the datasheet and everywhere on the internet I search I find the same ones over and over again.
Is the problem in AT responses that I'm not reading correctly? Or in parsing AT commands to the serial port?
Can anybody help me understand where I'm going wrong with this, or where I can look for to understand how to make this work?
I need to parse the pcap files and count the packets separately (TCP,UDP,IP). I found a lot of libraries for this like pcap, jnetpcap but I want to do this without using any external libraries.I do not need a code but a just a conceptual explanation.
Question
While parsing pcap files how should I distinguish between the frames(be it TCP,UDP,IP). I tried reading about the format but what I do not understand is how would I come to know about how many bytes should I read for a particular frame and how would i know what type of a frame is it.Because only once I am able to extract the packets separately I will be able to filter out other information.
You'd have to parse each frame separately and have a counter for each value you are trying to count. Assuming the capture you are examining is in pcap/pcapng format you might find libpcap helpful.
To give a quick run of what you might have to do (assuming the lower level is Ethernet without VLAN tags)
uint64_t ip_count, tcp_count, udp_count;
void parse_pkt(uint8_t *data, uint32_t data_len) {
uint8_t *ether_hdr = data;
uint16_t ether_type = ntohs(*(uint16_t *) (data + 12))
if (ether_type != 0x800) {
return;
}
ip_count += 1;
uint8_t *ip_hdr = data + 14;
protocol = ntohs(*(uint16_t *) (ip_hdr + 9))
//protocol is either udp/tcp/sctp...etc
if (protocol == 0x11) {
udp_count++;
} else if (protocol == 0x06) {
tcp_count++;
}
}
// foreach pkt from libpcap_open call parse_pkt with the data and data_len
This code is fragile. Jumping to direct offsets without the proper length and type checks is not a good idea.
My app "streams" content (fixed sized files, hence quotation marks) from an HTTP server into a local file. Then there is another component of the app that opens that same file and displays it (plays it).
This is done for caching purposes, so that when the same file is requested next time, it will no longer need to be downloaded from the server.
App's spec requires that all local content is encrypted (even with the most light weight encryption)
Question: has there been done any work, allowing one to simply redirect the stream to a library which will then save the stream encrypted into a file? And then, when I request the stream from the local file, the library returns an on the fly decrypted stream?
I've been searching for a solution with no results so far
Thanks
I ended up writing a custom solution that uses RC4 encryption from the built in Crypt library. It was surprisingly straight forward. Basically it involved creating a function that encrypts/decrypts chunks of NSData and then read/write those chunks to files... Here's the function that does the encryption in case someone else is interested:
- (NSData*)RC4EncryptDecryptWithKey:(NSString *)key operation:(CCOperation)operation
{
// convert to C string..
int keySize = [key length];
char keyPtr[keySize];
bzero(keyPtr, sizeof(keyPtr));
[key getCString:keyPtr
maxLength:sizeof(keyPtr)
encoding:NSUTF8StringEncoding];
// encode/decode
NSUInteger dataLength = [self length];
size_t bufferSize = dataLength;
void *buffer = malloc(bufferSize);
size_t numBytesOut = 0;
CCCryptorStatus cryptStatus = CCCrypt(operation,
kCCAlgorithmRC4,
kCCOptionECBMode,
keyPtr,
8,
NULL,
[self bytes],
dataLength,
buffer,
bufferSize,
&numBytesOut);
if (cryptStatus == kCCSuccess) {
return [NSData dataWithBytesNoCopy:buffer
length:numBytesOut
freeWhenDone:YES];
}
free(buffer);
return nil;
}
- (NSData*)RC4EncryptWithKey:(NSString*)key {
return [self RC4EncryptDecryptWithKey:key operation:kCCEncrypt];
}
- (NSData*)RC4DecryptWithKey:(NSString*)key {
return [self RC4EncryptDecryptWithKey:key operation:kCCDecrypt];
}
Obviously one could create something more secure (eg AES) or whatever (in fact I used examples of other encryption wrappers to write this one)
I wouldn't worry about encryption just because Apple says so.
Make this work how you want it (without encryption, it sounds like) and submit it for approval. If approved, you're good. If not, worry about it then. If your design requires you to make a decision now, your design might be flawed.