这里简单写一下 基于CocoaAsyncSocket的即时通讯，包括心跳机制。超时服务器自动踢出消极客户端。(服务器，客户端分开工程写)

一、服务器#####

1、新建一个类 SerViceAPP 用于开启服务器

#import <Foundation/Foundation.h>
@interface SerViceAPP : NSObject
-(void)openSerVice; //开启服务器
@end

#import "SerViceAPP.h"
#import "GCDAsyncSocket.h"
#import "ClientObj.h"
@interface SerViceAPP()<GCDAsyncSocketDelegate>

@property(nonatomic, strong)GCDAsyncSocket *serve;
@property(nonatomic, strong)NSMutableArray *arrayClient;
@property(nonatomic, strong)NSThread *checkThread;
@end

@implementation SerViceAPP
-(instancetype)init{
    if (self = [super init]) {
        self.serve = [[GCDAsyncSocket alloc] initWithDelegate:self delegateQueue:dispatch_get_global_queue(0, 0)];
        //开启个不死线程不断检测所连接的每个客户端的心跳
        self.checkThread = [[NSThread alloc]initWithTarget:self selector:@selector(checkClientOnline) object:nil];
        [self.checkThread start];
    }
    
    return self;
}
-(NSMutableArray *)arrayClient{
    if (!_arrayClient) {
        _arrayClient = [NSMutableArray array];
    }
    
    return _arrayClient;
}

-(void)openSerVice{
    
    NSError *error;
   BOOL sucess = [self.serve acceptOnPort:8088 error:&error];
    if (sucess) {
        NSLog(@"端口开启成功,并监听客户端请求连接...");
    }else {
        NSLog(@"端口开启失...");
    }
    //端口号port自己设置，动态端口的范围从1024到65535，
}

#pragma delegate

- (void)socket:(GCDAsyncSocket *)serveSock didAcceptNewSocket:(GCDAsyncSocket *)clientSocket{
    NSLog(@"%@ IP: %@: %zd 客户端请求连接...",clientSocket,clientSocket.connectedHost,clientSocket.connectedPort);
    // 1.将客户端socket保存起来
    ClientObj *client = [[ClientObj alloc]init];
    client.scocket = clientSocket;
    client.timeNew = [NSDate date];
    [self.arrayClient addObject:client];
    [clientSocket readDataWithTimeout:-1 tag:0];
}

- (void)socket:(GCDAsyncSocket *)clientSocket didReadData:(NSData *)data withTag:(long)tag  {
    NSString *clientStr = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"%@",clientStr);
    NSString *log = [NSString stringWithFormat:@"IP:%@ %zd data: %@",clientSocket.connectedHost,clientSocket.connectedPort,clientStr];
   
    for (ClientObj *socket in self.arrayClient) {
         if (![clientSocket isEqual:socket.scocket]) {
             //群聊 发送给其他客户端
             [self writeDataWithSocket:socket.scocket str:log];
         }else{
             ///更新最新时间
             socket.timeNew = [NSDate date];
         }
    }
    [clientSocket readDataWithTimeout:-1 tag:0];
}

- (void)socketDidDisconnect:(GCDAsyncSocket *)sock withError:(NSError *)err{
    NSLog(@"又下线");
    NSMutableArray *arrayNew = [NSMutableArray array];
    for (ClientObj *socket in self.arrayClient ) {
        if ([socket.scocket isEqual:sock]) {
            continue;
        }
        [arrayNew addObject:socket   ];
    }
    self.arrayClient = arrayNew;
}

-(void)exitWithSocket:(GCDAsyncSocket *)clientSocket{
//    [self writeDataWithSocket:clientSocket str:@"成功退出\n"];
//    [self.arrayClient removeObject:clientSocket];
//    
//    NSLog(@"当前在线用户个数:%ld",self.arrayClient.count);
}

- (void)socket:(GCDAsyncSocket *)sock didWriteDataWithTag:(long)tag{
    NSLog(@"数据发送成功..");
}

- (void)writeDataWithSocket:(GCDAsyncSocket*)clientSocket str:(NSString*)str{
    [clientSocket writeData:[str dataUsingEncoding:NSUTF8StringEncoding] withTimeout:-1 tag:0];
}

#pragma checkTimeThread
//这里设置35s检查一次 数组里所有的客户端socket 最后一次通讯时间,这样的话会有周期差（最多差35s），可以设置为1s检查一次，这样频率快
//开启线程 启动runloop 循环检测客户端socket最新time

- (void)checkClientOnline{
    @autoreleasepool {
        [NSTimer scheduledTimerWithTimeInterval:35 target:self selector:@selector(repeatCheckClinetOnline) userInfo:nil repeats:YES];
        [[NSRunLoop currentRunLoop]run];
    }
}

//移除 超过心跳时差的 client
- (void)repeatCheckClinetOnline{
    if (self.arrayClient.count == 0) {
        return;
    }
    NSDate *date = [NSDate date];
    NSMutableArray *arrayNew = [NSMutableArray array];
    for (ClientObj *socket in self.arrayClient ) {
        if ([date timeIntervalSinceDate:socket.timeNew]>30) {
            continue;
        }
        [arrayNew addObject:socket   ];
    }
    self.arrayClient = arrayNew;
}
@end

#import <Foundation/Foundation.h>
#import "GCDAsyncSocket.h"
@interface ClientObj : NSObject
@property(nonatomic, strong)GCDAsyncSocket *scocket;
@property(nonatomic, strong)NSDate *timeNew;//更新最新通讯时间
@end

二、客户端#####

#import "ViewController.h"
#import "GCDAsyncSocket.h"
@interface ViewController ()<GCDAsyncSocketDelegate>
@property(nonatomic,strong)GCDAsyncSocket *socket;
@property (weak, nonatomic) IBOutlet UITextField *mesage;
@property (weak, nonatomic) IBOutlet UIButton *sender;
@property (nonatomic, strong)NSThread *thread;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    GCDAsyncSocket *socket = [[GCDAsyncSocket alloc]initWithDelegate:self delegateQueue:dispatch_get_global_queue(0, 0)];
    [socket connectToHost:@"192.168.1.129" onPort:8088 error:nil];
    
    self.socket = socket;
    [self.sender addTarget:self action:@selector(sendmessage:) forControlEvents:UIControlEventTouchUpInside];
}

#pragma delegate

- (void)sendmessage:(UIButton*)sender{
    [self.socket writeData:[self.mesage.text dataUsingEncoding:NSUTF8StringEncoding ] withTimeout:-1 tag:0];
    
}

- (void)socket:(GCDAsyncSocket *)sock didReadData:(NSData *)data withTag:(long)tag{
    NSString *dataStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    
    NSLog(@"%@",dataStr);
    [sock readDataWithTimeout:-1 tag:0];
}

- (void)socket:(GCDAsyncSocket *)sock didConnectToHost:(NSString *)host port:(uint16_t)port {
    NSLog(@"连接成功");
    
    [self.socket readDataWithTimeout:-1 tag:0];
    //开启线程发送心跳
    [self.thread start];
}

-(void)socketDidDisconnect:(GCDAsyncSocket *)sock withError:(NSError *)err{
    NSLog(@"断开连接 %@",err);
    //再次可以重连
    if (err) {
//         [self.socket connectToHost:sock.connectedHost onPort:sock.connectedPort error:nil];
    }else{
//        正常断开
    }
   
}

//开启不死线程不断发送心跳

- (void)threadStart{
    @autoreleasepool {
        [NSTimer scheduledTimerWithTimeInterval:29 target:self selector:@selector(heartBeat) userInfo:nil repeats:YES];
        [[NSRunLoop currentRunLoop]run];
    }
}

- (void)heartBeat{
    [self.socket writeData:[@"heart" dataUsingEncoding:NSUTF8StringEncoding ] withTimeout:-1 tag:0];
}

- (NSThread*)thread{
    if (!_thread) {
        _thread = [[NSThread alloc]initWithTarget:self selector:@selector(threadStart) object:nil];
    }
    return _thread;
}

git demo:
<a href="https://github.com/qhf012607/Socket" title="https://github.com/qhf012607/Socket">an example</a>

最后

可以通过使用终端 命令:telnet 192.168.1.1 8088（你的IP端口号）模拟没有发送心跳的客户端 多开几个客户端模拟群聊，服务器会自动踢出超时消极的客户端.

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谢谢#.