Write DLL code
New construction
New empty project project
Click OK. Then right-click the project and select New item.
Select New again, select the C++ file, change it to MySocketClient.c, and select Add.
At this point, the new construction is completed.
Then right-click the project and select Properties to change the configuration type to dynamic library (.dll)
Write the header file mysocketClient.h
#ifndef _INC_MYSOCKETCLIENT_H_
#define _INC_MYSOCKETCLIENT_H_
#define Import_SSS
#ifdef Import_SSS
#define API _declspec(dllexport)
#else
#define API _declspec(dllimport)
#endif
#ifdef _cplusplus//extern”C” tells the compiler: this is a library file written in C, please link them in C style.
extern “C” {
#endif // _cplusplus
API// Export functions for external calls.
int socketClient_Init(void **handle);
API
int socketClient_Send(void *handle, unsigned char *buf, int buflen);
API
int socketClient_Recv(void *handle, unsigned char *buf, int *buflen);
API
int socketClient_Destory(void *handle);
#ifdef _cplusplus
}
#endif // _cplusplus
#endif //_INC_MYSOCKETCLIENT_H_
Write MySocketClient. C
#define _CRT_SECURE_NO_WARNINGS
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include “MySocketClient.h”
typedef struct _Sck_Handle
{
char version[16];
char ip[16];
int port;
unsigned char *p;
int len;
}Sck_Handle; // Define the structure of Handle.
int socketClient_Init(void **handle)
{
int ret = 0;
Sck_Handle *tmpHandle = NULL;
if (handle == NULL)
{
ret = -1;
printf(“[socketClient_Init] err %d handle=NULL \n”, ret);
return ret;
}
tmpHandle = (Sck_Handle *)malloc(sizeof(Sck_Handle));
if (tmpHandle == NULL)
{
ret = -2;
printf(“[socketClient_Init] err:%d malloc err \n”, ret);
}
memset(tmpHandle, 0, sizeof(Sck_Handle)); // Initializes the structure.
Strcpy (tmpHandle – > version, “1.0.0.1”);
Strcpy (tmpHandle – > IP, “192.168.12.121”);
tmpHandle->port = 11111;
*handle = tmpHandle;
return ret;
}
Sending Socket packets
//__declspec(dllexport)
int socketClient_Send(void *handle, unsigned char *buf, int buflen)
{
int ret = 0;
Sck_Handle *tmpHandle = NULL;
if (handle == NULL || buf == NULL || buflen <= 0)
{
ret = -2;
printf(“func socketclient_send() err :%d (handle == NULL || buf==NULL || buflen <=0 ) \n”, ret);
return ret;
}
tmpHandle = (Sck_Handle *)handle;
tmpHandle->len = buflen;
tmpHandle->p = (unsigned char *)malloc(buflen);
if (tmpHandle->p == NULL)
{
ret = -2;
printf(“func socketclient_send() err :%d malloc len:%d \n”, ret, buflen);
return ret;
}
memcpy(tmpHandle->p, buf, buflen); // Cache data to memory
Printf (” Received send data is %s \n”, tmpHandle->p);
return ret;
}
Socket Packet Acceptance
//__declspec(dllexport)
int socketClient_Recv(void *handle, unsigned char *buf, int *buflen)
{
int ret = 0;
Sck_Handle *tmpHandle = NULL;
if (handle == NULL || buf == NULL || buflen == NULL)
{
ret = -2;
printf(“func socketclient_recv() err :%d (handle == NULL || buf==NULL || buflen==NULL ) \n”, ret);
return ret;
}
tmpHandle = (Sck_Handle *)handle;
memcpy(buf, tmpHandle->p, tmpHandle->len);
*buflen = tmpHandle->len; // Indirect assignment tells the caller the length of the received data
Printf (” Data length is %d \n”, tmpHandle->len);
return ret;
}
Socket environment Release
//__declspec(dllexport)
int socketClient_Destory(void *handle)
{
int ret = 0;
Sck_Handle *tmpHandle = NULL;
if (handle == NULL)
{
return -1;
}
tmpHandle = (Sck_Handle *)handle;
if (tmpHandle->p ! = NULL)
{
free(tmpHandle->p); // Free the memory space pointed to by the pointer to the structure member field
}
free(tmpHandle); // Release the structure inside the body
return 0;
}
Then right-click to compile the project. You can see the generated DLL in the Debug folder
Call the DLL
Create a C++ console application
After the creation, place the compiled DLL files, lib files, and H files under the project.
Right-click the project properties and change the character set to use a multi-byte character set.
Here is the code to invoke the DLL.
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <windows.h>
#include <iostream>
using namespace std;
// define a pointer function
typedef int(*SOCLETCLIENT_INIT)(void **handle);
typedef int(*SOCKETCLIENT_SEND)(void *handle, unsigned char *buf, int buflen);
typedef int(*SOCKETCLIENT_RECV)(void *handle, unsigned char *buf, int *buflen);
typedef int(*SOCKETCLIENT_DESTORY)(void *handle);
int main()
{
HINSTANCE hInstance;
hInstance = LoadLibrary(“MySocketClient.dll”);
SOCLETCLIENT_INIT socketClient_Init= (SOCLETCLIENT_INIT)GetProcAddress(hInstance, “socketClient_Init”);
SOCKETCLIENT_SEND socketClient_Send=(SOCKETCLIENT_SEND)GetProcAddress(hInstance, “socketClient_Send”);;
SOCKETCLIENT_RECV socketClient_Recv= (SOCKETCLIENT_RECV)GetProcAddress(hInstance, “socketClient_Recv”);;
SOCKETCLIENT_DESTORY socketClient_Destory= (SOCKETCLIENT_DESTORY)GetProcAddress(hInstance, “socketClient_Destory”);;
unsigned char buf[1024];
int buflen;
unsigned char out[1024];
int outlen;
void *handle = NULL;
int ret = 0;
strcpy((char *)buf, “aaaaAAAAAFFffffffdddddddd”);
buflen = 9;
// The client initializes and retrieves the upper and lower handle
ret = socketClient_Init(&handle /*out*/);
if (ret ! = 0)
{
printf(“func socketclient_init() err:%d \n “, ret);
goto End;
}
// The client sends packets
ret = socketClient_Send(handle /*in*/, buf /*in*/, buflen /*in*/);
if (ret ! = 0)
{
printf(“func socketclient_send() err:%d \n “, ret);
goto End;
}
// The client receives the message
ret = socketClient_Recv(handle /*in*/, out /*in*/, &outlen/*in out*/);
if (ret ! = 0)
{
printf(“func socketclient_recv() err:%d \n “, ret);
goto End;
}
Printf (” Received data length is %d \n”,outlen);
End:
// The client releases resources
ret = socketClient_Destory(handle/*in*/);
if (hInstance ! = NULL)
{
FreeLibrary(hInstance);
hInstance = NULL;
}
printf(“hello… \n”);
system(“pause”);
return 0;
}
Code links: download.csdn.net/download/hh…