An example of network communication based on TCP / IP protocol -- file transmission

One 、 Server code ：MyServer.cpp

// MyServer.cpp :  Defines the entry point for the console application .
//

#include "stdafx.h"
#include <iostream>
using namespace std;

#include<stdlib.h>
#include<winsock2.h>// Reference header file 
#pragma comment(lib,"ws2_32.lib")// Reference library file 

// maximum connection 
#define g_MaxConnect 20
int g_Connect = 0;

struct sock_params
{
    
	SOCKET hsock;
	int nSockIndex;
};

// Thread implementation function 
DWORD WINAPI threadpro(LPVOID pParam)
{
    
	sock_params* sockPam = (sock_params*)pParam;
	SOCKET hsock = sockPam->hsock;
	int nSockIndex = sockPam->nSockIndex;

	char aIndex[4];
	_itoa_s(nSockIndex, aIndex, 10);

	char buffer[1024];
	char sendBuffer[1024];
	if(hsock != INVALID_SOCKET)
	{
    
		cout<<" client  "<< nSockIndex << "  Join the server !" <<endl;
	}
	
	//  Set the receive buffer size 
	int nRecvBufLen = 1024* 1024; // The default setting is 1024K
	int nStaus = setsockopt(hsock ,SOL_SOCKET,SO_RCVBUF,(const char*)&nRecvBufLen,sizeof(int));
	if (nStaus == SOCKET_ERROR)
	{
    
		hcDebugLog(_T("ZLY: Failed to set receive buffer size ！"));
	}

	//  Set the send buffer size 
	int nSendBufLen = 1024* 1024; // The default setting is 1024K
	nStaus = setsockopt(hsock ,SOL_SOCKET,SO_SNDBUF,(const 		char*)&nSendBufLen,sizeof(int));
	if (nStaus == SOCKET_ERROR)
	{
    
		hcDebugLog(_T("ZLY: Failed to set send buffer size ！"));
	}
	
	// Circularly receive the contents of the sent file 
	int nErrorNum = 0;
	while (1)
	{
    
		//  The server receives the file name data 
		FileName fn;
		memset(&fn, 0, sizeof(FileName));
		int nRecvSize = recv(clientSocket, (char*)&fn, sizeof(fn), 0);
		if (sizeof(fn) != nRecvSize)
		{
    
			if (nRecvSize != 0 && nErrorNum <= MAX_ERROR_NUM)
			{
    
				printf(" Failed to receive file name ！ Error code :%d\n", WSAGetLastError());
				nErrorNum++;
				continue;
			}
			else
			{
    
				break;
			}
		}

		char chPath[_MAX_PATH];
		memset(chPath, 0, sizeof(char)*_MAX_PATH);
		strcpy_s(chPath, sizeof(chPath), fn.serverDir);
		int len = strlen(chPath);
		if (chPath[len - 1] != '\\')
		{
    
			chPath[len] = '\\';
			len++;
		}

		strcat_s(chPath, fn.dir);
		len = strlen(chPath);
		if (chPath[len - 1] != '\\')
		{
    
			chPath[len] = '\\';
			len++;
		}

		//  Create the corresponding directory 
		g_lock.Lock();
		CreateDir(chPath);
		g_lock.UnLock();
		strcat_s(chPath, fn.Fname);

		//  create a file 
		FILE* fp = NULL;
		errno_t err = fopen_s(&fp, chPath, "wb");
		if (err != 0)
		{
    
			printf(" Failed to create file ：%s,  Error code :%d\n", chPath, GetLastError());
			continue;
		}

		//  The length of the file received by the server 
		long long nSize;
		nRecvSize = recv(clientSocket, (char*)&nSize, sizeof(nSize), 0);
		if (sizeof(nSize) != nRecvSize)
		{
    
			if (fp)
			{
    
				fclose(fp);
				fp = NULL;
			}

			if (nRecvSize != 0 && nErrorNum <= MAX_ERROR_NUM)
			{
    
				printf(" Failed to receive file length ！ Error code :%d\n", WSAGetLastError());
				nErrorNum++;
				continue;
			}
			else
			{
    
				break;
			}
		}

		//  Circular acceptance of file content 
		int num;
		char buff[MAX_PACK_SIZE];
		while (nSize > 0)
		{
    
			if (nSize >= MAX_PACK_SIZE)
			{
    
				num = recv(clientSocket, buff, MAX_PACK_SIZE, 0);
			}
			else
			{
    
				num = recv(clientSocket, buff, nSize, 0);
			}

			fwrite(buff, (int)num, 1, fp);
			nSize -= num;
			memset(buff, 0, sizeof(char)*MAX_PACK_SIZE); // take buff Empty 
		}

		//  Close file 
		if (fp)
		{
    
			fclose(fp);
			fp = NULL;
		}

		//  Send file acceptance success status 
		int nRecvStatus = 0;
		send(clientSocket, (char*)&nRecvStatus, sizeof(int), 0);
	}

	return 0;
}

// The main function 
void main()
{
    
	WSADATA wsd;// Definition WSADATA object 
	WSAStartup(MAKEWORD(2,2),&wsd);
	SOCKET m_SockServer;
	sockaddr_in serveraddr;

	sockaddr_in serveraddrfrom;
	SOCKET m_Server[g_MaxConnect];

	serveraddr.sin_family = AF_INET;// Set the server address 
	serveraddr.sin_port = htons(4600);// Set the port number 
	serveraddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
	m_SockServer = socket(AF_INET,SOCK_STREAM,0);
	int nStatus = bind(m_SockServer,(sockaddr*)&serveraddr,sizeof(serveraddr));
	if (nStatus == 0)
	{
    
		cout << " Server started successfully !" <<endl;
	}
	else
	{
    
		cout << " Failed to start the server !" <<endl;
		return;
	}

	int iLisRet = 0;
	int len = sizeof(sockaddr);
	while(1)
	{
    
		iLisRet = listen(m_SockServer,0);// monitor 
		m_Server[g_Connect] = accept(m_SockServer,(sockaddr*)&serveraddrfrom,&len);

		// Agree to connect 
		if(m_Server[g_Connect] != INVALID_SOCKET)
		{
    
			if(g_Connect > g_MaxConnect-1)
			{
    
				char WarnBuf[50]=" Number of client connections : Transfinite !";
				int ires = send(m_Server[g_Connect],WarnBuf,sizeof(WarnBuf),0);
			}
			else
			{
    
				char cIndex[4];
				_itoa_s(g_Connect, cIndex, 10);
				char buf[50]=" Your server ID: ";
				strcat_s(buf, cIndex);

				int ires = send(m_Server[g_Connect],buf,sizeof(buf),0);// Send characters past 
				//cout << buf <<endl;

				HANDLE m_Handel;	// Thread handle 
				DWORD nThreadId=0;	// Threads ID

				sock_params sockPam;
				sockPam.hsock = m_Server[g_Connect];
				sockPam.nSockIndex = g_Connect;

				m_Handel = (HANDLE)::CreateThread(NULL,0,threadpro,&sockPam,0,&nThreadId);
				CloseHandle(m_Handel);
			}

			++g_Connect;
		}
	}

	WSACleanup();
}

Two 、 client ：MyClient.cpp

// MyClient.cpp :  Defines the entry point for the console application .
//

#include "stdafx.h"
#include<iostream>

using namespace std;

#include<stdlib.h>
#include<stdio.h>
#include"winsock2.h"
#include<time.h>
#pragma comment(lib,"ws2_32.lib")

void main()
{
    
	WSADATA wsd;// Definition WSADATA object 
	WSAStartup(MAKEWORD(2,2),&wsd);
	SOCKET m_SockClient;
	sockaddr_in clientaddr;

	clientaddr.sin_family = AF_INET;	// Set the server address 
	clientaddr.sin_port = htons(4600);  // Set the server port number 
	clientaddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
	m_SockClient = socket(AF_INET,SOCK_STREAM,0);
	
	if (m_SockClient == INVALID_SOCKET)
	{
    
		printf("Sock  initialization failed : %d\n", WSAGetLastError());
		WSACleanup();
		return ;
	}
	//  Get the size of sending buffer and receiving buffer 
	{
    
		int optlen = 0;
		int optval = 0;

		optlen = sizeof(optval);
		getsockopt(m_SockClient, SOL_SOCKET, SO_SNDBUF, (char*)&optval, &optlen);
		printf("send buf len is %d\n",optval);           //64 position   Default send buffer 64k
		getsockopt(m_SockClient, SOL_SOCKET, SO_RCVBUF, (char*)&optval, &optlen);
		printf("Recv buf len is %d\n",optval);          //64 position   Default receive buffer 64k
	}
	
	//  Set the receive buffer size 
	int nRecvBufLen = 1024* 1024; // The default setting is 1024K
	int nStaus = setsockopt(pSocketData->clientSocket,SOL_SOCKET,SO_RCVBUF,(const char*)&nRecvBufLen,sizeof(int));
	if (nStaus == SOCKET_ERROR)
	{
    
		hcDebugLog(_T("ZLY: Failed to set receive buffer size ！"));
	}

	//  Set the send buffer size 
	int nSendBufLen = 1024* 1024; // The default setting is 1024K
	nStaus = setsockopt(pSocketData->clientSocket,SOL_SOCKET,SO_SNDBUF,(const 		char*)&nSendBufLen,sizeof(int));
	if (nStaus == SOCKET_ERROR)
	{
    
		hcDebugLog(_T("ZLY: Failed to set send buffer size ！"));
	}
    
	int nSuccess = connect(m_SockClient,(sockaddr*)&clientaddr,sizeof(clientaddr));// Connection timeout 
	if (nSuccess == 0)
	{
    
		cout<<" Successfully connected to the server !"<<endl;
	}
	else
	{
    
		cout<<" Failed to connect to server !"<<endl;
		return;
	}

	char buffer[1024];
	char inBuf[1024];
	int num = 0;
	num = recv(m_SockClient,buffer,1024,0);// Blocking 
	if(num > 0)
	{
    
		cout << /*"Receive from server:"<<*/ buffer<<endl;

		char* pResult = strstr(buffer, " Transfinite ");
		if (pResult != NULL)
		{
    
			cout<<" The number of server connections exceeds the limit , Unavailable ！"<<endl;
			system("pause"); 
			return;
		}
		
		// Pass file name 
		char filename[256];

		FILE* m_fp;
		errno_t err = fopen_s(&m_fp, filename, "rb");
		if (err != 0)
		{
    
			strlog.Format(_T(" file “%s” Open the failure , Error code ：0x%X"), filename, GetLastError());
			return -1;
		}
		
		//  Send file name 
		if (sizeof(filename) != send(m_sock, &filename, sizeof(filename), 0))
		{
    
			strLog.Format(_T(" file “%s” Failed to send file name , Error code ：%d."), (LPCTSTR)CString(m_fn.Fname), WSAGetLastError());
			cout << strLog <<endl;
			fclose(m_fp);
			m_fp = NULL;
			return -1;
		}
		fseek(m_fp, 0, SEEK_END);
		long long nSize = ftell(m_fp);
		fseek(m_fp, 0, SEEK_SET);
		
		//  Get file length , Send file length ( abandoned )
		if (sizeof(nSize) != send(m_sock, (char*)&nSize, sizeof(nSize), 0))
		{
    
			printf(_T(" Failed to send file length , Error code ：%d."), WSAGetLastError());
			fclose(m_fp);
			m_fp = NULL;
			return -1;
		}
		
		// Send a file 
		/*  Sending multiple files in a loop seems to make an error  HANDLE hFile = CreateFile(lpszFilePath,GENERIC_READ,FILE_SHARE_READ,0,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,0); TransmitFile(m_Socket,hFile,0,TRANS_FILE_LENGTH,NULL,NULL,TF_DISCONNECT); CloseHandle(hFile); */

		//  Loop the file 
		size_t nNum;
		while (1)
		{
    
			nNum = fread(m_temp, 1, 1024*500, m_fp);
			if (nNum == 0)
				break;

			if (nNum != send(m_sock, m_temp, (int)nNum, 0))
			{
    
				strLog.Format(_T(" file “%s” Failed to send file data , Error code :%d."), (LPCTSTR)CString(m_fn.Fname), WSAGetLastError());
				fclose(m_fp);
				m_fp = NULL;
				return -1;
			}

			memset(m_temp, 0, sizeof(char)*1024*500);
		}

		//  Close file 
		fclose(m_fp);
		m_fp = NULL;
		
		// Receive the data fed back by the server 
		int recv_len = recv(m_SockClient,buffer,1024,0);
		if(recv_len>=0)
		{
    
			cout<< buffer <<endl;
		}
	}
}