服务端，即写入端

#include <iostream>
#include <string.h>
#define BUF_SIZE 1024
#ifdef _WIN32
#include <windows.h>
#define SHARENAME L"shareMemory"
HANDLE g_MapFIle;
LPVOID g_baseBuffer;
#else
#define SHARENAME "shareMemory"
#include <sys/shm.h>
#include <sys/time.h>
#include <unistd.h>
int g_shmid = -1;
char* g_baseBuffer = NULL;
#endif

void CloseShareMemory()
{
#ifdef _WIN32
	if (g_baseBuffer) {
		FlushViewOfFile(g_baseBuffer, BUF_SIZE);
		UnmapViewOfFile(g_baseBuffer);
		g_baseBuffer = NULL;
	}
	if (g_MapFIle) {
		CloseHandle(g_MapFIle);
		g_MapFIle = NULL;
	}
#else
	shmdt(g_baseBuffer);
	shmctl(g_shmid, IPC_RMID, 0);//删除
#endif
}

bool CreateShareMemory()
{
#ifdef _WIN32
	if (g_MapFIle)
		CloseShareMemory();
	g_MapFIle = CreateFileMapping(
		INVALID_HANDLE_VALUE,	//物理文件句柄
		NULL,					//默认安全级别
		PAGE_READWRITE,			//可读可写
		0,						//高位文件大小
		BUF_SIZE,				//地位文件大小
		SHARENAME				//共享内存名称
	);
	if (g_MapFIle) {
		//映射缓存区视图,得到指向共享内存指针
		g_baseBuffer = MapViewOfFile(
			g_MapFIle,				//共享内存句柄
			FILE_MAP_ALL_ACCESS,	//可读可写许可
			0,
			0,
			BUF_SIZE
		);
		memset(g_baseBuffer, 0, BUF_SIZE);//初始化 置 0 
		return true;
	}
#else
	key_t key = ftok(SHARENAME, 0);
	g_shmid = shmget(key, BUF_SIZE, IPC_CREAT | 0666);
	if (g_shmid != -1) {
		g_baseBuffer = (char*)shmat(g_shmid, 0, 0);
		return true;
	}
#endif
	return false;
}

int main()
{
	//创建
	if (!CreateShareMemory()) {
		std::cout << "CreateShareMemory error!\n";
		return -1;
	}
	//写入数据
	char ch[1024];
	while (1) {
		std::cout << "写入数据或输入exit退出:" << std::endl;
		std::cin >> ch;
		if (0 == strcmp(ch, "exit"))
			break;
		memcpy(g_baseBuffer, ch, 1024);
	}
	//断开 关闭
	CloseShareMemory();

	return 0;
}

客户端，即读取端

#include <iostream>
#include <string.h>
#define BUF_SIZE 1024
#ifdef _WIN32
#include <windows.h>
#define SHARENAME L"shareMemory"
HANDLE g_MapFIle;
LPVOID g_baseBuffer;
#else
#define SHARENAME "shareMemory"
#include <sys/shm.h>
#include <sys/time.h>
#include <unistd.h>
int g_shmid = -1;
char* g_baseBuffer = NULL;
#endif

void CloseShareMemory()
{
#ifdef _WIN32
	if (g_baseBuffer) {
		FlushViewOfFile(g_baseBuffer, BUF_SIZE);
		UnmapViewOfFile(g_baseBuffer);
		g_baseBuffer = NULL;
	}
	if (g_MapFIle) {
		CloseHandle(g_MapFIle);
		g_MapFIle = NULL;
	}
#else
	shmdt(g_baseBuffer);
	//shmctl(g_shmid, IPC_RMID, 0);//删除
#endif
}

bool OpenShareMemory()
{
#ifdef _WIN32
	if (g_baseBuffer)
		CloseShareMemory();
	g_MapFIle = OpenFileMapping(FILE_MAP_ALL_ACCESS, 0, SHARENAME);
	if (g_MapFIle) {
		g_baseBuffer = MapViewOfFile(g_MapFIle, FILE_MAP_ALL_ACCESS, 0, 0, BUF_SIZE);
		return true;
	}
#else
	key_t key = ftok(SHARENAME, 0);
	g_shmid = shmget(key, BUF_SIZE, IPC_CREAT | 0666);
	if (g_shmid != -1) {
		g_baseBuffer = (char*)shmat(g_shmid, 0, 0);
		return true;
	}
#endif
	return false;
}

int main()
{
	while (1) {
		//打开
		if (!OpenShareMemory()) {
			std::cout << "CreateShareMemory error!\n";
			return -1;
		}
		//读取
		char str[1024];
		memcpy(str, g_baseBuffer, 1024);
		memset(g_baseBuffer, 0, BUF_SIZE);
		if(str[0] != '\0')
			std::cout << "read  value:" << str << std::endl;

		//断开 关闭
		CloseShareMemory();
#ifdef _WIN32
		Sleep(100);
#else

#endif
	}

	return 0;
}

windows演示图

linux 演示图