iPhone - Strange behaviour when '&' is included in HTTP request body - iphone

Question

I've got a very strange problem related to sending POST request from my iPhone app.
The app needs to send the HTTP post data to a third-party service. Request is XML and it'll get XML response. Here's my code for sending the request:
-(void)sendRequest:(NSString *)aRequest
{
//aRequest parameter contains the XML string to send.
//this string is already entity-encoded
isDataRequest = NO;
//the following line will created string REQUEST=<myxml>
NSString *httpBody = [NSString stringWithFormat:#"%#=%#",requestString,aRequest];
//I'm not sure what this next string is doing, frankly, as I didn't write this code initially
httpBody = [(NSString*)CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault, (CFStringRef)httpBody, NULL, CFSTR("+"), kCFStringEncodingUTF8) autorelease];
NSData *aData = [httpBody dataUsingEncoding:NSUTF8StringEncoding];
NSMutableURLRequest *request = [[[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:kOOURLRequest]] autorelease];
[request setHTTPBody:aData];
[request setHTTPMethod:#"POST"];
self.feedURLConnection = [[[NSURLConnection alloc] initWithRequest:request delegate:self] autorelease];
}
This works perfectly well as long as the request XML doesn't contain & symbol, for example, this XML request:
<?xml version="1.0"?>
<request type="search" group="0" language="en" version="2.5.2">
<auth>
<serial>623E1579-AC18-571B-9022-3659764542E7</serial>
</auth>
<data>
<location>
<lattitude>51.528536</lattitude>
<longtitude>-0.108865</longtitude>
</location>
<search>archive</search>
</data>
</request>
is sent as expected and the correct response is received as expected.
However, when the request contains & character (specifically in the "search" element) - like so:
<?xml version="1.0"?>
<request type="search" group="0" language="en" version="2.5.2">
<auth>
<serial>623E1579-AC18-571B-9022-3659764542E7</serial>
</auth>
<data>
<location>
<lattitude>51.528536</lattitude>
<longtitude>-0.108865</longtitude>
</location>
<search>& archive</search>
</data>
</request>
Only everything up to the & character is sent to the server. The server doesn't seem to receive anything beyond this character. Note that I have a pretty much the same code working in an Android app and everything is working correctly, so it's not a problem on the server.
Any ideas how I can get this fixed would be greatly appreciated!

Answer 1

Thanks to Zaph's comment, I finally sorted it. I used WireShark to see what was actually sent to the server and discovered that the request wasn't encoded completely. In the final HTTP body the actual symbol & was present (part of &). This naturally didn't work very well on the server side, because it was receiving something like:
REQUEST=first_half_of_request&second_half_of_request
When the server decoded the POST variables, & was taken as the separator of variables, therefore the REQUEST variable was only set to the first_half_of_request - everything up to the & char.
The solution was quite simple. In line
httpBody = [(NSString*)CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault, (CFStringRef)httpBody, NULL, CFSTR("+"), kCFStringEncodingUTF8) autorelease];
replace CFSTR("+") with CFSTR("+&") to encode & as well. Now this, combined with entity encoding (& for &), resulted in the correct data being sent to the server and the correct response being received.