代码： dllmain.cpp:

/* Replace "dll.h" with the name of your header */
#include "dll.h"
#include <windows.h>

DLLIMPORT int ConnectToSurver(const char*ip,const char*str_send,char*receive) {
	// 初始化socket dll。
	WORD winsock_version = MAKEWORD(2,2);
	WSADATA wsa_data;
	if (WSAStartup(winsock_version, &wsa_data) != 0) {
		printf("Failed to init socket!\n");
		return -1;
	}
	
	SOCKET client_socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (client_socket == INVALID_SOCKET) {
		printf("Failed to create server socket!\n");
		return -1;
	}
	
	struct sockaddr_in server_addr;
	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(PORT);
	server_addr.sin_addr.S_un.S_addr = inet_addr(ip);
	if (connect(client_socket, (LPSOCKADDR)&server_addr, sizeof(server_addr)) == SOCKET_ERROR) {
		printf("Failed to connect server: %ld !\n", GetLastError());
		return -1;
	}
	
	char recv_data[BUFFER_SIZE+1]="";
	
	while (true) {
		//char data[BUFFER_SIZE+1];
		//printf("Input data: ");
//		scanf("%s",data);
		if (send(client_socket, str_send, strlen(str_send), 0) < 0) {
			//printf("Failed to send data!\n");
			break;
		}
		
		int ret = recv(client_socket, recv_data, BUFFER_SIZE, 0);
		if (ret < 0) {
			//printf("Failed to receive data!\n");
			break;
		}
		recv_data[ret]=0; // correctly ends received string
		
		//printf("Receive data from server: \"%s\"\n",recv_data);
		
		break;
	}
	receive=recv_data;
	closesocket(client_socket);
	WSACleanup();
	
	return -1;
}

dll.h:

#ifndef _DLL_H_
#define _DLL_H_

#if BUILDING_DLL
#define DLLIMPORT __declspec(dllexport)
#else
#define DLLIMPORT __declspec(dllimport)
#endif
#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <winsock2.h>  
#define PORT 8888
//#define SERVER_IP "192.168.0.102"
#define  BUFFER_SIZE 4196
DLLIMPORT char*ConnectToSurver(const char*ip,const char*str_send);
#endif