TCP是底層通訊協議，定義的是資料傳輸和連線方式的規範。TCP協議，傳輸控制協議（Transmission Control Protocol，縮寫為：TCP）是一種面向連線的、可靠的、基於位元組流的通訊協議。講到TCP協議就繞不開套接字Socket。這也是搞軟體開發經常接觸的技術點。 套接字Socket是通訊的基石，是支援TCP/IP協議的網路通訊的基本操作單元。它是網路通訊過程中端點的抽象表示，包含進行網路通訊必須的五種資訊：連線使用的協議，本地主機的IP地址，本地程式的協議埠，遠地主機的IP地址，遠地程式的協議埠。 建立Socket連線時，可以指定使用的傳輸層協議，Socket可以支援不同的傳輸層協議（TCP或UDP），當使用TCP協議進行連線時，該Socket連線就是一個TCP連線。

在網路通訊中，從架構設計和應用需要具備抽象思維。讓閱讀者和使用者非常清晰的理解設計思路。採用割裂思維。形象的比喻成大炮和炮彈。大炮。發射裝置分HTTP和TCP。收發機制不同。每種程式語言都有自己固定的API實現。炮彈就是二進位制流資料。不固定完全可以DIY。就是我們常說的通訊協議。所謂“協議”是雙方共同遵守的規則。協議有語法、語義、時序三要素。炮彈抽象轉實體就是Gk8ByteMaker。具體實現參閱。[網路通訊1：位元組流的封裝]( http://blog.itpub.net/69975060/viewspace-2693162/ )。針對大炮發射裝置實現。其實許多程式語言都不需要自己造輪子。甚至很多框架支援、比如Java有名氣的MINA框架。作為程式設計者應該需要探索的慾望。自己實現過對底層的理解更透徹。領悟過記憶才更深刻。曾經有個面試者就理直氣壯說Socket底層就是可以直接傳輸類物件。因為他工作接觸的都是完善的框架。直接物件導向程式設計。缺乏捅破窗戶紙窺探下底層真正的實現原理。

專案使用C++實現網路TCP通訊(tcpnet)。其中Gk8Socket是實現底層Socket通訊。Gk8TcpService是提供介面服務。方便使用者方便快捷的使用。同時發射裝置肯定需要炮彈。也使用了Gk8ByteMaker。每種程式語言實現都有差異。這裡僅拋磚引玉。重點還是理解思維和原理。記憶容易忘記。思維不容易忘記。

C++實現網路Socket類：Gk8Socket.h

```c++
#ifndef _GK8SOCKET_H_
#define _GK8SOCKET_H_

#pragma once
#include "Gk8Env.h"

#if(GK8_TARGET_PLATFORM==GK8_PLATFORM_WIN32)
	#include <winsock2.h>
	typedef int				socklen_t;
#else
	#include <sys>
	#include <netinet>
	#include <netdb.h>
	#include <fcntl.h>
	#include <unistd.h>
	#include <sys>
	#include <sys>
	#include <arpa>
	typedef int				SOCKET;

//[定義一些建立標記宏]
	#define INVALID_SOCKET	-1
	#define SOCKET_ERROR	-1
#endif

class Gk8Socket
{
protected://[類保護屬性]
	SOCKET m_iSocket;		//[SCOKET套接字]
	fd_set m_fdR;			//[SCOKET資訊]
	
public://[類公共屬性]
	Gk8Socket(SOCKET iSocket=INVALID_SOCKET);
	~Gk8Socket();

static int Init();
	static int Clean();

Gk8Socket& operator=(SOCKET iSocket);
	operator SOCKET();
	
	bool Create(int af, int type, int protocol = 0);
	bool Connect(const char* ip, unsigned short port);
	bool Bind(unsigned short port);
	bool Listen(int backlog = 5);
	bool Accept(Gk8Socket& s, char* fromip = NULL);
	int Select();
	int Send(const char* buf, int len, int flags=0);
	int Recv(char* buf, int len, int flags=0);
	int Close();
	int GetError();
};

#endif
```

C++實現網路Socket類：Gk8Socket.cpp

```c++
#include "Gk8Socket.h"
#include "Gk8OperSys.h"
#include <stdio.h>

#if(GK8_TARGET_PLATFORM==GK8_PLATFORM_WIN32)
#pragma comment(lib, "wsock32")
#endif

Gk8Socket::Gk8Socket(SOCKET iSocket)
{
	m_iSocket=iSocket;
}

Gk8Socket::~Gk8Socket()
{
}

//[初始化SOCKET]
int Gk8Socket::Init()
{
#if(GK8_TARGET_PLATFORM==GK8_PLATFORM_WIN32)
	WSADATA wsaData;
	WORD version = MAKEWORD(2, 0);
	int nRet = WSAStartup(version, &wsaData);//[WinSock啟動]
	if(nRet)
	{
		_GK8ERR<0)
		{
			return -2;
		}else
		{
			return -3;
		}
	}
}
//[傳送資料:直接傳送]
int Gk8Socket::Send(const char* buf, int len, int flags)
{
	int bytes;
	int count = 0;
	while(count<len bytes="(GK8_INT)send(m_iSocket,buf+count,len-count,flags);" if="" return="" count="" int="" gk8socket::recv="" buf="" len="" flags="" gk8socket::close="" gk8socket::geterror="" c="" __gk8tcpservice_h__="" once="">
#include <semaphore.h>

#if(GK8_TARGET_PLATFORM==GK8_PLATFORM_IOS||GK8_TARGET_PLATFORM==GK8_PLATFORM_ANDROID)
#include <sys>
#endif

class Gk8TcpService:public Gk8BaseObj
{
	DECLARE_TOSPP_MAP;
private:
	pthread_t m_nPId;					//[執行緒ID]
	GK8_BOOL m_bCreatePthread;			//[建立了執行緒]
	Gk8ByteMaker m_iRequestData;		//[TCP請求資料]
public:
	Gk8Socket m_iSocket;
	Gk8Str m_iHostIpStr;				//[伺服器IP]
	GK8_INT m_nPort;					//[服務埠]

pthread_mutex_t mt_TcpResponseMutex;//[TCP響應互斥體]
	Gk8ByteMaker m_iTcpData;			//[TCP反饋資料]

private:
	static void* start_thread(void*);	//[靜態成員函式,相當於C中的全域性函式]
	GK8_VOID TcpSocketFailCallBack(GK8_INT nFailCode);
	GK8_VOID TcpSocketSuccCallBack();
	GK8_VOID TcpRequestStarted();
	GK8_VOID DispatcherReceiveMessage();
public:
	Gk8TcpService();
	~Gk8TcpService();
	
	GK8_BOOL TOSPPFUNC Build(GK8_LPCSTR lpHostIp,GK8_INT nPort);

GK8_VOID TOSPPFUNC SendMessage(Gk8ByteMaker* pRequestData);
	GK8_VOID TOSPPFUNC PutMessage(Gk8ByteMaker* pRequestData);
	GK8_VOID TOSPPFUNC SendCachedMessage();

GK8_VOID TOSPPFUNC Close();			//[函式中止當前執行緒]

static GK8_VOID TcpClientTick();
};

#endif
```

C++實現Tcp服務類：Gk8TcpService.cpp

```c++
#include "Gk8TcpService.h"

//[TCP SOCKET錯誤編碼]
enum TCPSOCKETFAILERRORCODE
{
	TCPCODE_PTHREAD_FAIL=0,
	TCPCODE_SOCKET_INIT_FAIL,
	TCPCODE_SOCKET_CREATE_FAIL,
	TCPCODE_SOCKET_CONNECT_FAIL,
	TCPCODE_SOCKET_SEND_FAIL,
	TCPCODE_END
};

static Gk8Var sg_iTcpSocketFailEventFun("OnTcpSocketFail");		//[TCPSOCKET失敗資訊]
static Gk8Var sg_iTcpSocketSuccEventFun("OnTcpSocketSucc");		//[TCPSOCKET成功資訊]
static Gk8Var sg_iTcpReceiveMessageFun("ReceiveMessage");		//[接收網路資訊]
static Gk8SortMap sg_iTcpSocketMap;								//[委託MAP]//[用來管理回撥的]

/////////////////////////////////////////////CLASS-TOSPP////////////////////////////////////////////////////
BEGIN_TOSPP_MAP(Gk8TcpService,Gk8BaseObj)
	TOSPP_FUNC(Gk8TcpService,Build,'b',"sd","Build(lpHostIp,nPort)")
	TOSPP_FUNC(Gk8TcpService,SendMessage,' ',"p","SendMessage(iRequestDataPtr)")
	TOSPP_FUNC(Gk8TcpService,PutMessage,' ',"p","PutMessage(iRequestDataPtr)")
	TOSPP_FUNC(Gk8TcpService,SendCachedMessage,' '," ","SendCachedMessage()")
	TOSPP_FUNC(Gk8TcpService,Close,' ',"","Close()")
END_TOSPP_MAP()

/////////////////////////////////////[套接字邏輯]///////////////////////////////////////////////
Gk8TcpService::Gk8TcpService()
{
	pthread_mutex_init(&mt_TcpResponseMutex,NULL);
	sg_iTcpSocketMap.AddItem((GK8_PTR_TYPE)this,0);
	m_bCreatePthread=false;
}
Gk8TcpService::~Gk8TcpService()
{
	pthread_mutex_destroy(&mt_TcpResponseMutex);
	sg_iTcpSocketMap.RemoveItem((GK8_PTR_TYPE)this);
}
//[套接字失敗回撥]
GK8_VOID Gk8TcpService::TcpSocketFailCallBack(GK8_INT nFailCode)
{
	OnCall(sg_iTcpSocketFailEventFun,Gk8Var()<<nfailcode gk8_void="" gk8tcpservice::tcpsocketsucccallback="" oncall="" gk8_bool="" gk8tcpservice::build="" lphostip="" nport="" m_irequestdata.destroy="" m_itcpdata.destroy="" m_ihostipstr="lpHostIp;" m_nport="nPort;" int="" errcode="0;" do="" pthread_attr_t="" tattr="" if="" return="" false="" pthread_attr_destroy="" tcpsocketfailcallback="" m_bcreatepthread="true;" true="" void="" gk8tcpservice::start_thread="" arg="" gk8tcpservice="" ptcpservice="(Gk8TcpService*)arg;" gk8socket="" isocket="" ptcpservice-="">TcpSocketFailCallBack(TCPCODE_SOCKET_INIT_FAIL);
		return NULL;
	}
	//[建立套接字]
	if(!iSocket.Create(AF_INET,SOCK_STREAM,0))
	{
		pTcpService->TcpSocketFailCallBack(TCPCODE_SOCKET_CREATE_FAIL);
		return NULL;
	}
	//[連線套接字]
	if(!iSocket.Connect(pTcpService->m_iHostIpStr,pTcpService->m_nPort))
	{
		pTcpService->TcpSocketFailCallBack(TCPCODE_SOCKET_CONNECT_FAIL);
		return NULL;
	}
	pTcpService->m_iSocket=iSocket;
	//[通知連線成功]
	pTcpService->TcpSocketSuccCallBack();
	//[迴圈監聽.接收資料]
	Gk8ByteMaker sl_iRecvBuf;
	sl_iRecvBuf.WriteAlloc(1024*1024);
	GK8_INT nRecvLen=0;
	while(true)
	{
		//[表示伺服器端有訊息推送過來.會接受HTTP的請求返回]
		if(iSocket.Select()==-2)
		{
			sl_iRecvBuf.ClearStream();
			nRecvLen=iSocket.Recv((GK8_LPSTR)sl_iRecvBuf.GetBuf(),1024*1024,0);
			if(nRecvLen<=0) continue;
			//[多執行緒控制]
			pthread_mutex_lock(&pTcpService->mt_TcpResponseMutex);
			pTcpService->m_iTcpData.WriteBuf(sl_iRecvBuf.GetBuf(),nRecvLen);
			pthread_mutex_unlock(&pTcpService->mt_TcpResponseMutex);
		}
	}
	return NULL;
}

//[傳送訊息]
GK8_VOID Gk8TcpService::SendMessage(Gk8ByteMaker* pRequestData)
{
	pRequestData->ShiftTo(m_iRequestData);
	TcpRequestStarted();
}
//[把二進位制流重組成新的物件]
GK8_VOID Gk8TcpService::PutMessage(Gk8ByteMaker* pRequestData)
{
	pRequestData->ShiftTo(m_iRequestData);
}

GK8_VOID Gk8TcpService::SendCachedMessage()
{
	TcpRequestStarted();
}

//[開始TCP請求]
GK8_VOID Gk8TcpService::TcpRequestStarted()
{
	GK8_INT nSendLen=m_iRequestData.GetStreamSize();
	if(m_iSocket.Send((GK8_LPCSTR)m_iRequestData.GetBuf(),nSendLen)!=nSendLen)
	{
		TcpSocketFailCallBack(TCPCODE_SOCKET_SEND_FAIL);
		return ;
	}
	m_iRequestData.ClearStream();
}
//[向指令碼派發訊息]
GK8_VOID Gk8TcpService::DispatcherReceiveMessage()
{
	if(m_iTcpData.GetStreamSize()<2*sizeof(GK8_WORD)) return;
	
	pthread_mutex_lock(&mt_TcpResponseMutex);
	Gk8Var iByteMakerVar(&m_iTcpData,m_iTcpData.GetObjId());
	OnCall(sg_iTcpReceiveMessageFun,iByteMakerVar);
	//[把資料往前提]
	m_iTcpData.Pack();
	pthread_mutex_unlock(&mt_TcpResponseMutex);
}
//[停止SOCKET]
GK8_VOID Gk8TcpService::Close()
{
	m_iSocket.Close();

#if(GK8_TARGET_PLATFORM==GK8_PLATFORM_ANDROID)
	_GK8ERR<DispatcherReceiveMessage();
	}
}
```</nfailcode></sys></semaphore.h></len></stdio.h></arpa></sys></sys></unistd.h></fcntl.h></netdb.h></netinet></sys></winsock2.h>

網路通訊2：TCP通訊實現

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