客户端我们使用iPhone应用程序，画面比较简单。点击发送按钮，给服务器发送一些字符串过去。点击接收按钮就会从服务器读取一些字符串，并且显示在画面上。
有关客户端应用的UI部分不再介绍了，我们直接看代码部分，Socket客户端可以采用CFStream或NSStream实现，CFStream 实现方式与服务器端基本一样。为了给读者介绍更多的知识，本例我们采用NSStream实现。NSStream实现采用Objective-C语言，一些 面向对象的类。
下面我们看看客户端视图控制器ViewController.h
#import <CoreFoundation/CoreFoundation.h>
#include <sys/socket.h>
#include <netinet/in.h>
#define PORT 9000
@interface ViewController : UIViewController<NSStreamDelegate>
{
int flag ; //操作标志 0为发送 1为接收
}
@property (nonatomic, retain) NSInputStream *inputStream;
@property (nonatomic, retain) NSOutputStream *outputStream;
@property (weak, nonatomic) IBOutlet UILabel *message;
- (IBAction)sendData:(id)sender;
- (IBAction)receiveData:(id)sender;
@end
定义属性inputStream和outputStream，它们输入流NSInputStream和输出流NSOutputStream类。它们与服务器CFStream实现中的输入流CFReadStreamRef和输出流CFWriteStreamRef对应的。
视图控制器ViewController.m的初始化网络方法initNetworkCommunication代码：
- (void)initNetworkCommunication
{
CFReadStreamRef readStream;
CFWriteStreamRef writeStream;
CFStreamCreatePairWithSocketToHost(NULL,
(CFStringRef)@”192.168.1.103″, PORT, &readStream, &writeStream); ①
_inputStream = (__bridge_transfer NSInputStream *)readStream; ②
_outputStream = (__bridge_transfer NSOutputStream*)writeStream; ③
[_inputStream setDelegate:self]; ④
[_outputStream setDelegate:self]; ⑤
[_inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop]
forMode:NSDefaultRunLoopMode]; ⑥
[_outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop]
forMode:NSDefaultRunLoopMode]; ⑦
[_inputStream open]; ⑧
[_outputStream open]; ⑨
}
点击发送和接收按钮触发的方法如下：
/* 点击发送按钮 */
- (IBAction)sendData:(id)sender {
flag = 0;
[self initNetworkCommunication];
}
/* 点击接收按钮 */
- (IBAction)receiveData:(id)sender {
flag = 1;
[self initNetworkCommunication];
}
它们都调用initNetworkCommunication方法，并设置操作标识flag，如果flag为0发送数据，flag为1接收数据。
流的状态的变化触发很多事件，并回调NSStreamDelegate协议中定义的方法stream:handleEvent:，其代码如下：
-(void)stream:(NSStream *)theStream handleEvent:(NSStreamEvent)streamEvent {
NSString *event;
switch (streamEvent) {
case NSStreamEventNone:
event = @”NSStreamEventNone”;
break;
case NSStreamEventOpenCompleted:
event = @”NSStreamEventOpenCompleted”;
break;
case NSStreamEventHasBytesAvailable:
event = @”NSStreamEventHasBytesAvailable”;
if (flag ==1 && theStream == _inputStream) {
NSMutableData *input = [[NSMutableData alloc] init];
uint8_t buffer[1024]; ①
int len;
while([_inputStream hasBytesAvailable]) ②
{
len = [_inputStream read:buffer maxLength:sizeof(buffer)]; ③
if (len > 0)
{
[input appendBytes:buffer length:len];
}
}
NSString *resultstring = [[NSString alloc]
initWithData:input encoding:NSUTF8StringEncoding];
NSLog(@”接收:%@”,resultstring);
_message.text = resultstring;
}
break;
case NSStreamEventHasSpaceAvailable:
event = @”NSStreamEventHasSpaceAvailable”;
if (flag ==0 && theStream == _outputStream) {
//输出
UInt8 buff[] = ”Hello Server!”; ④
[_outputStream write:buff maxLength: strlen((const char*)buff)+1]; ⑤
//关闭输出流
[_outputStream close];
}
break;
case NSStreamEventErrorOccurred:
event = @”NSStreamEventErrorOccurred”;
[self close]; ⑥
break;
case NSStreamEventEndEncountered:
event = @”NSStreamEventEndEncountered”;
NSLog(@”Error:%d:%@”,[[theStream streamError] code],
[[theStream streamError] localizedDescription]);
break;
default:
[self close]; ⑦
event = @”Unknown”;
break;
}
NSLog(@”event??%@”,event);
}
在读取数据分支（NSStreamEventHasBytesAvailable）中，代码第①行为读取数据准备缓冲区，本例中设置的是1024个字节，这个大小会对流的读取有很多的影响。第②行代码使用hasBytesAvailable方法判断是否流有数据可以读，如果有可读数据就进行循环读取。第③行代码使用流的read:maxLength:方法读取数据到缓冲区，第1个参数是缓冲区对象buffer，第2个参数是读取的缓冲区的字节长度。
在写入数据分支（NSStreamEventHasSpaceAvailable）中，代码第④行是要写入的数据，第⑤行代码 [_outputStream write:buff maxLength: strlen((const char*)buff)+1]是写如数据方 法。
第⑥和第⑦行代码[self close]调用close方法关闭，close方法代码如下：
-(void)close
{
[_outputStream close];
[_outputStream removeFromRunLoop:[NSRunLoop currentRunLoop]
forMode:NSDefaultRunLoopMode];
[_outputStream setDelegate:nil];
[_inputStream close];
[_inputStream removeFromRunLoop:[NSRunLoop currentRunLoop]
forMode:NSDefaultRunLoopMode];
[_inputStream setDelegate:nil];
}