Encoding puzzles with sockets in different languages - php

Question

I have this below code written in PHP responsible for the server socket, specifically by writing messages to certain sockets:
header('Content-Type: text/html; charset=utf-8');
const PAYLOAD_LENGTH_16 = 126;
const PAYLOAD_LENGTH_63 = 127;
const OPCODE_CONTINUATION = 0;
for ($i = 0; $i < $frameCount; $i++) {
// fetch fin, opcode and buffer length for frame
$fin = $i != $maxFrame ? 0 : self::FIN;
$opcode = $i != 0 ? self::OPCODE_CONTINUATION : $opcode;
$bufferLength = $i != $maxFrame ? $bufferSize : $lastFrameBufferLength;
// set payload length variables for frame
if ($bufferLength <= 125) {
$payloadLength = $bufferLength;
$payloadLengthExtended = '';
$payloadLengthExtendedLength = 0;
}
elseif($bufferLength <= 65535) {
$payloadLength = self::PAYLOAD_LENGTH_16;
$payloadLengthExtended = pack('n', $bufferLength);
$payloadLengthExtendedLength = 2;
} else {
$payloadLength = self::PAYLOAD_LENGTH_63;
$payloadLengthExtended = pack('xxxxN', $bufferLength); // pack 32 bit int, should really be 64 bit int
$payloadLengthExtendedLength = 8;
}
// set frame bytes
$buffer = pack('n', (($fin | $opcode) << 8) | $payloadLength).$payloadLengthExtended.substr($message, $i * $bufferSize, $bufferLength);
And below I have the code in Objective-C responsible for receiving these messages from the socket server:
NSInteger len = 0;
uint8_t buffer[4096];
while ([inputStream hasBytesAvailable]) {
len = [inputStream read:buffer maxLength:sizeof(buffer)];
if (len > 0) {
[self.data appendBytes:buffer length:len];
[self.log insertText:[NSString stringWithFormat:#"Log: Received a message from server:\n\n"]];
NSLog(#"Received a message from server...");
}
}
when all bytes are received I run the following command to turn the data into a file:
[self.data writeToFile:#"dataComes.txt" options:NSDataWritingAtomic error:nil]
The Problem
We will send a large file in JSON format for objective-c, with that he will receive that information and will generate a file called dataComes.txt, I can see the JSON file normally but except for some strange characters such as:
~ or ~Â or â-Û
These strange characters always shows at the beginning of each block messages that Objective-C receives (Yes, the socket server and TCP divide large messages into blocks of messages).
What is the cause of this problem and how it could solve this?

Answer 1

SOLUTION 1: Filtering
I can filter out unwanted characters that may come, but it will also filter out some words that have accentuation:
NSCharacterSet *notAllowedChars = [[NSCharacterSet characterSetWithCharactersInString:#"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ[]{}:,'"] invertedSet];
NSString *resultString = [[total componentsSeparatedByCharactersInSet:notAllowedChars] componentsJoinedByString:#" "];
SOLUTION 2: Stop using sockets
I have tried many ways to send data to my app, the only one that worked was to send the data separately (a loop of one JSON), but to works I had to put my code (PHP) to sleep using sleep(1) (and I believe this is not good) because if not Objective-C recognizes that this data is a single package.
In this case, or my code have problems, or the programming of socket in objective-c was not very well done and has inconsistencies (bug). What remains for me to do with my connections through normal requests via web server (which I do not think it's a good idea, since I have to do this every 3 seconds in a 5 minute time interval).
SOLUTION 3: FILTERING + UNICODE
On the server side I can filter all special characters and create a specific combination for it example:
Hello é world to Hello /e001/ world
And in my app I can filter this combination and change to the real format....