GCDAsyncSocke 分为
一. Configuration 配置

1.1代理的设置

1.2线程的设置

1.3IPV4，IPV6的设置

二. Accepting 接收

2.1.监听端口起点

- (BOOL)acceptOnPort:(uint16_t)port error:(NSError **)errPtr
{
return [self acceptOnInterface:nil port:port error:errPtr];
}

- (BOOL)acceptOnInterface:(NSString *)inInterface port:(uint16_t)port error:(NSError **)errPtr
{
LogTrace();

// Just in-case interface parameter is immutable.
//防止参数被修改
NSString *interface = [inInterface copy];

__block BOOL result = NO;
__block NSError *err = nil;

// CreateSocket Block
// This block will be invoked within the dispatch block below.
//创建socket的Block
int(^createSocket)(int, NSData*) = ^int (int domain, NSData *interfaceAddr) {

//创建TCP的socket
int socketFD = socket(domain, SOCK_STREAM, 0);

//一系列错误判断
...
// Bind socket
//用本地地址去绑定
status = bind(socketFD, (const struct sockaddr *)[interfaceAddr bytes], (socklen_t)[interfaceAddr length]);

//监听这个socket
//第二个参数是这个端口下维护的socket请求队列，最多容纳的用户请求数。
status = listen(socketFD, 1024);
return socketFD;
};

// Create dispatch block and run on socketQueue

dispatch_block_t block = ^{ @autoreleasepool {

//一系列错误判断
...

//判断ipv4 ipv6是否支持
...

//得到本机的IPV4 IPV6的地址
[self getInterfaceAddress4:&interface4 address6:&interface6 fromDescription:interface port:port];
...

//判断可以用IPV4还是6进行请求
...

// Create accept sources
//创建接受连接被触发的source
if (enableIPv4)
{
//接受连接的source
accept4Source = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, socket4FD, 0, socketQueue);

//事件句柄
dispatch_source_set_event_handler(accept4Source, ^{ @autoreleasepool {

//拿到数据，连接数
unsigned long numPendingConnections = dispatch_source_get_data(acceptSource);

LogVerbose(@"numPendingConnections: %lu", numPendingConnections);

//循环去接受这些socket的事件(一次触发可能有多个连接)
while ([strongSelf doAccept:socketFD] && (++i < numPendingConnections));

}});

//取消句柄
dispatch_source_set_cancel_handler(accept4Source, ^{
//...
//关闭socket
close(socketFD);

});

//开启source
dispatch_resume(accept4Source);
}

//ipv6一样
...

//在scoketQueue中同步做这些初始化。
if (dispatch_get_specific(IsOnSocketQueueOrTargetQueueKey))
block();
else
dispatch_sync(socketQueue, block);

//...错误判断
//返回结果
return result;
}

三. Connecting 连接

四. Disconnecting 断开

五. Diagnostics 诊断

六. Reading 读取

七. Writing   写入
八. Security 安全
九. Advanced
十. Utilities

socket通讯----GCDAsyncSocke 解读