上一篇实现了简单的 Server 端程序，服务端通过 void WriteStreamClientCallBack(CFWriteStreamRef stream, CFStreamEventType eventType, void* clientCallBackInfo) 函数向客户端发送“你好，客户端！”的消息，如果客户端接收成功的话就会显示“你好，客户端！”；需要显示服务端发送过来的消息，那么就需要定义一个UILabel输出口（IBOutlet）来显示消息；客户端还需要添加两个按钮，一个用来接收服务端消息的动作事件方法 receiveData：和发送客户端“收到啦，服务端”消息的动作事件方法 sendData：；添加关联就可以了，比较简单，下面来看一下具体实现的代码：

     ViewController.h

#import <UIKit/UIKit.h>

#import <CoreFoundation/CoreFoundation.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define PORT 8734       //将端口设置为8734，可以根据具体情况改变

@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;    //在客户端显示来自服务端的消息

- (IBAction)sendData:(id)sender;      //发送客户端的消息
- (IBAction)receiveData:(id)sender;   //接收来自服务端的消息

@end

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
}

//初始化客户端网络连接
- (void)initNetworkCommunication
{
    
    CFReadStreamRef readStream;
    CFWriteStreamRef writeStream;
    //这里需要填写 IP 地址，根据自己路由可以用的 IP来定，这里是192.168.1.103，如果不知道可以下载 IP 扫描器
    CFStreamCreatePairWithSocketToHost(NULL, (CFStringRef)@"192.168.1.103", PORT, &readStream, &writeStream);
    
    self.inputStream = (__bridge_transfer NSInputStream *)readStream;  //将CFStream对象转化为NSStream对象
    self.outputStream = (__bridge_transfer NSOutputStream
                     *)writeStream;              //将CFStream对象转化为NSStream对象
    [self.inputStream setDelegate:self];
    [self.outputStream setDelegate:self];
    [self.inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop]
                            forMode:NSDefaultRunLoopMode];    //NSStream 方法 scheduleInRunLoop: 设置 Run Loop
    [self.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop]
                             forMode:NSDefaultRunLoopMode];
    [self.inputStream open];   //NSStream 的 open 方法来打开数据流对象
    [self.outputStream open];
    
}

//关闭数据流操作
-(void)close
{
    [self.outputStream close];
    [self.outputStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.outputStream setDelegate:nil];
    [self.inputStream close];
    [self.inputStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.inputStream setDelegate:nil];
}

//从客户端发送数据事件方法
- (IBAction)sendData:(id)sender {
    flag = 0;   //表示发送
    [self initNetworkCommunication];
    
}

//从服务端接收数据事件方法
- (IBAction)receiveData:(id)sender {
    flag = 1;   //表示接收
    [self initNetworkCommunication];
    
}

-(void)stream:(NSStream *)theStream handleEvent:(NSStreamEvent)streamEvent {
    NSString *event;
    switch (streamEvent) {
        case NSStreamEventNone:  //没有事件发生
            event = @"NSStreamEventNone";
            break;
        case NSStreamEventOpenCompleted:  //成功打开流
            event = @"NSStreamEventOpenCompleted";
            break;
        case NSStreamEventHasBytesAvailable:   //这个流有数据可以读，在读取数据时使用
            event = @"NSStreamEventHasBytesAvailable";
            if (flag ==1 && theStream == _inputStream) {
                NSMutableData *input = [[NSMutableData alloc] init];
                uint8_t buffer[2048]; //读取数据准备缓冲区，本例中设置的是2048字节，这个大小会对流的读取有很大影响   
                int len;
                while([self.inputStream hasBytesAvailable])
                {
                    len = [self.inputStream read:buffer maxLength:sizeof(buffer)];  //读取数据到缓冲区
                    if (len > 0)
                    {
                        [input appendBytes:buffer length:len];
                    }
                }
                NSString *resultstring = [[NSString alloc] initWithData:input encoding:NSUTF8StringEncoding];
                NSLog(@"接收:%@",resultstring);
                self.message.text = resultstring;
            }
            break;
        case NSStreamEventHasSpaceAvailable:   //这个流可以接收数据的写入，在写数据时使用
            event = @"NSStreamEventHasSpaceAvailable";
            if (flag ==0 && theStream == _outputStream) {
                //输出
                UInt8 buff[] = "收到啦，服务端！";       //向服务端发送的消息
                [self.outputStream write:buff maxLength: strlen((const char*)buff)+1];   //向服务端写入数据方法
                 //必须关闭输出流否则，服务器端一直读取不会停止，
                [self.outputStream close];
            }
            break;
        case NSStreamEventErrorOccurred:      //数据流发生错误
            event = @"NSStreamEventErrorOccurred";
            [self close];
            break;
        case NSStreamEventEndEncountered:     //数据流结束
            event = @"NSStreamEventEndEncountered";
            NSLog(@"Error:%d:%@",[[theStream streamError] code], [[theStream streamError] localizedDescription]);
            break;
        default:
            [self close];
            event = @"Unknown";
            break;
    }

}

@end

     如有哪些不对的地方，欢迎指出！

iOS 中基于Socket 的 C/S 结构的网络通信（下）