iOS ISO-8583 message sending

Question

I'm an iOS developer. I need to send a message in ISO-8583 standard, via socket server.

I have established connection with server, and it is working well. The server works this way : when message comes to it in correct format (but with incorrect data, eg. wrong PIN), it responds with proper error code. When message comes in wrong format, the server doesn't respond at all ;)

So, knowing that my connection works fine (tested), I have following problem : I need to send ISO8583 message to server. The message must have those fields :

• SI (2 bytes - size of whole message)
• TPDU (it must be 12345 - documetation says)
• Detail (more info below)
• EOT (specification - sign "0D")

In below example, we are using :

• MTI - 0200
• Account number - 6019 5300 0601 9592
• Code - 700000
• Terminal ID - 35959551
• PIN - 880088 (needs to have two SPACES appedned to the end (docs says))

Here are documentation specifications :

• Field 2 - Card number, length - 19 (3 length + 16 number), format LLVAR
• Field 3 - Processing code, length - 6, format NUMBER
• Field 12 - Time (hhmmss), length - 6, format NUMBER
• Field 13 - Date (mmdd), length - 4, format NUMBER
• Field 41 - Terminal ID, length - 8, format ALPHANUMERICAL
• Field 52 - PIN, length - 16, format HEX

So, fields 2,3,12,13,41 and 52 must be set.

I used two methods :

1) using external library : https://github.com/mordoskull/Objective-ISO8583 - using many different combinations of data, it doesn't work. My usage :

   ISOMessage *isoMessage1 = [[ISOMessage alloc] init];
   NSString *tpdu = @"0102030405";
  [isoMessage1 setMTI:@"0200"];
  isoMessage1.bitmap = [[ISOBitmap alloc] initWithGivenDataElements:@[@"DE02", @"DE03", @"DE12", @"DE13", @"DE41", @"DE52"] configFileName:nil];
  [isoMessage1 addDataElement:@"DE02" withValue:cardNumber configFileName:nil];
  [isoMessage1 addDataElement:@"DE03" withValue:@"700000" configFileName:nil];
  [isoMessage1 addDataElement:@"DE12" withValue:transactionTime configFileName:nil];
  [isoMessage1 addDataElement:@"DE13" withValue:transactionDate configFileName:nil];
  [isoMessage1 addDataElement:@"DE41" withValue:@"35959551" configFileName:nil];  //TID - 35959551
  [isoMessage1 addDataElement:@"DE52" withValue:@"880088" configFileName:nil];

2) manually setting all fields like this :

//CARD NUMBER
NSData *card = [cardNumber dataUsingEncoding:NSUTF8StringEncoding];

//TPDU
NSMutableData *TPDU = [[NSMutableData alloc] init];
[TPDU appendBytes:"\x01\x02\x03\x04\x05" length:5];

//TRANSACTION CODE
NSData *transactionCode = [[NSString stringWithFormat:@"%x",700000] dataUsingEncoding:NSUTF8StringEncoding];

//TIME AND DATE
NSData *time = [[NSString stringWithFormat:@"%x",[transactionTime intValue]] dataUsingEncoding:NSUTF8StringEncoding];
NSData *date = [[NSString stringWithFormat:@"%x",[transactionDate intValue]] dataUsingEncoding:NSUTF8StringEncoding];

//PIN
NSData *PIN = [[NSString stringWithFormat:@"%@  ",self.pinField.text] dataUsingEncoding:NSASCIIStringEncoding];

//TID
NSData *TID = [@"35959551" dataUsingEncoding:NSASCIIStringEncoding];

//MTI
NSMutableData *MTI = [[NSMutableData alloc] init];
[MTI appendBytes:"\x02\x00" length:2];

//BITMAP
NSArray* fields = [NSArray arrayWithObjects:@2, @3,
                   @12, @13, @41, @52, nil];
NSMutableArray* binary = [NSMutableArray new];
for(int i=0 ; i<64 ; ++i) {
    binary[i] = @"0";
}
for(int j = 0; j<[fields count]; ++j)
{
    binary[[fields[j] intValue]-1] = @"1";
}

NSMutableString * bitmap = [[NSMutableString alloc] init];
for (NSObject * obj in binary)
{
    [bitmap appendString:[obj description]];
}
NSData *bitmapByte = [bitmap dataUsingEncoding:NSUTF8StringEncoding];

NSMutableData *request = [[NSMutableData alloc] init];
[request appendData:TPDU];
[request appendData:MTI];
[request appendData:bitmapByte];
[request appendData:card];
[request appendData:transactionCode];
[request appendData:time];
[request appendData:date];
[request appendData:TID];
[request appendData:PIN];

NSData *SI = [[NSString stringWithFormat:@"00%lu",(unsigned long)[request length]] dataUsingEncoding:NSUTF8StringEncoding];

NSMutableData* fullRequest = [[NSMutableData alloc] init];
[fullRequest appendData:SI];
[fullRequest appendData:request];

I know that Card Number field must have three-digit length appended in front of it, and I know every other specs about ISO8583.

I managed to get NSData that looks like this in Log :

Printing description of fullRequest:
<30303131 39010203 04050200 30313130 30303030 30303031 31303030 30303030 30303030 30303030     30303030 30303030 30303030 31303030 30303030 30303031 30303030 30303030 30303030 30313636 30313935     33303030 36303139 35393261 61653630 31393232 37346231 33353935 39353531 38383030 38382020>

The same message, not converted to NSData, looks like this : 
009001020304050200601800000080100001660195300060195927000001131041201359595513838303038382020

And server doesn't respond at all, so I must be sending wrong formatted message.

Can somebody help me how to correctly format the message?

Answer 1

Finally managed to do it myslef. Here is a code for setting the parameters (in case somebody needs it) :

NSDate *currentTime = [NSDate date]; NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];

//get current Time
[dateFormatter setDateFormat:@"hhmmss"];
NSString *transactionTime = [dateFormatter stringFromDate: currentTime];
transactionTime = [transactionTime stringByReplacingOccurrencesOfString:@":" withString:@""];

//get current Date
[dateFormatter setDateFormat:@"MMdd"];
NSString *transactionDate = [dateFormatter stringFromDate:currentTime];

NSString* cardNumber = [[NSUserDefaults standardUserDefaults] objectForKey:@"cardNumber"];

//TID
NSData *TID = [@"35959551" dataUsingEncoding:NSASCIIStringEncoding];
//PIN
NSData *PIN = [[NSString stringWithFormat:@"%@",self.pinField.text] dataUsingEncoding:NSASCIIStringEncoding];
//TPDU
NSMutableData *TPDU = [[NSMutableData alloc] init];
[TPDU appendBytes:"\x01\x02\x03\x04\x05" length:5];
//MTI
NSMutableData *MTI = [[NSMutableData alloc] init];
[MTI appendBytes:"\x02\x00" length:2];
//TRANSACTION CODE
NSString *transactionCode = @"700000";
NSData *trCode = [self convertToData:transactionCode];
//CARD NUMBER
NSString *cardWithLength = [@"16" stringByAppendingString:cardNumber];
NSData *card = [self convertToData:cardWithLength];
//TIME AND DATE
NSData *time = [self convertToData:transactionTime];
NSData *date = [self convertToData:transactionDate];
//BITMAP
NSString *mapa = @"6018000000801000";
NSData *mapaData = [self convertToData:mapa];

NSMutableData *request = [[NSMutableData alloc] init];
[request appendData:TPDU];
[request appendData:MTI];
[request appendData:mapaData];
[request appendData:card];
[request appendData:trCode];
[request appendData:time];
[request appendData:date];
[request appendData:TID];
[request appendData:PIN];

NSString *SI = [NSString stringWithFormat:@"00%lu",(unsigned long)[request length]];
NSData *SIData = [self convertToData:SI];

NSMutableData* fullRequest = [[NSMutableData alloc] init];
[fullRequest appendData:SIData];
[fullRequest appendData:request];