Using NSStreams For A TCP Connection Without NSHost Q: Given that +getStreamsToHost:port:inputStre

Using NSStreams For A TCP Connection Without NSHost

Q:  Given that +getStreamsToHost:port:inputStream:outputStream: is not supported on iOS, how can I create NSStreams for a TCP connection to a named host?

A: You can do this by exploiting the toll-free bridge between NSStream and CFStream. Use CFStreamCreatePairWithSocketToHost to create CFStreams to the host, and then cast the resulting CFStreams to NSStreams.

Listing 1 shows an example of this. It adds a category to NSStream that implements a replacement for +getStreamsToHost:port:inputStream:outputStream:.

Listing 1  A category to create TCP streams to a named host

@interface NSStream (QNetworkAdditions)

+ (void)qNetworkAdditions_getStreamsToHostNamed:(NSString *)hostName

port:(NSInteger)port

inputStream:(out NSInputStream **)inputStreamPtr

outputStream:(out NSOutputStream **)outputStreamPtr;

@end

@implementation NSStream (QNetworkAdditions)

+ (void)qNetworkAdditions_getStreamsToHostNamed:(NSString *)hostName

port:(NSInteger)port

inputStream:(out NSInputStream **)inputStreamPtr

outputStream:(out NSOutputStream **)outputStreamPtr

{

CFReadStreamRef readStream;

CFWriteStreamRef writeStream;

assert(hostName != nil);

assert( (port > 0) && (port < 65536) );

assert( (inputStreamPtr != NULL) || (outputStreamPtr != NULL) );

readStream = NULL;

writeStream = NULL;

CFStreamCreatePairWithSocketToHost(

NULL,

(__bridge CFStringRef) hostName,

port,

((inputStreamPtr != NULL) ? &readStream : NULL),

((outputStreamPtr != NULL) ? &writeStream : NULL)

);

if (inputStreamPtr != NULL) {

*inputStreamPtr = CFBridgingRelease(readStream);

}

if (outputStreamPtr != NULL) {

*outputStreamPtr = CFBridgingRelease(writeStream);

}

}

@end

---

NSStream 真的就是 CFNetwork 上的一层简单的 Objective-C 封装。但 iOS 中的 NSStream 不支持 NShost，这是一个缺陷，苹果也意识到这问题了（ http://developer.apple.com/library/ios/#qa/qa1652/_index.html），我们可以通过 NSStream 的扩展函数来实现该功能：