Prevent stops application with NSStream in polling mode

Question

I have implemented a client-server transferring from Windows desktop application to iPhone App. I transfer data using NSStream in polling mode (synchronous).

CFReadStreamRef readStream;
CFWriteStreamRef writeStream;

CFStreamCreatePairWithSocketToHost(NULL, (CFStringRef)urlStr, portNo, &readStream, &writeStream);

inputStream = (NSInputStream *)readStream;
outputStream = (NSOutputStream *)writeStream;

[inputStream open];
[outputStream open];

All works fine, but when I attempt to connect an inexistent server or a disconnected server or the port number/ip address is wrong, the WRITE method of NSOutputStream object, stops the application execution.

const uint8_t *str = (uint8_t *) [strRichiesta cStringUsingEncoding:NSASCIIStringEncoding];
[outputStream write:str maxLength:strlen((char*)str)]; 

Is it possible to manage the method by inserting timeout control? If yes, how can I do?

I think that the same problem occurs also with READ method of NSInputStream object.

Could someone help me, please?