一. 程序说明
1.本程序通过 UDP 来传输文件及其管理元数据（文件名、大小和日期等），包括client.cpp和server.cpp，分别是客户端程序和服务端程序。
2.文件以二进制形式传输。
3.由客户端指定文件目录，将文件传送到服务端，除了文件名之外，附带传送文件大小、创建时间等信息。
4.获取文件大小和创建日期的详细程序可以看C++获取文件的创建时间和大小
5.客户端发送完毕后，向服务端发送一条“end”信息，服务端受到后停止监听。
6.通过UDP传输比TCP快，但是UDP不如TCP稳定，可能出现丢包和乱序的情况。这里通过“发-收-发”的方式防止丢包和乱序，即客户端每发送一条消息，服务端收到后都会回信一条，受到回信后，客户端再继续发送，没有受到则报错。还有一种实现方式是，利用多线程发送信息，给每次发送的信息编号，服务端检查收到的信息的编号，以此判断是否出现乱序或丢包。(暂未完成)
二. 代码实现
client.cpp:
/*
客户端程序
客户端给服务端发送文件，包含管理元数据（文件名、大小和日期）
*/
#include<iostream>
#include<WinSock2.h>
#include<winsock.h>
#include<Windows.h>
#include<string>
#include<cstring>
#include <fstream>
#include <io.h>
#pragma comment(lib,"ws2_32.lib")
#define BUF_SIZE 1024
#define SERVER_ID "127.0.0.1"
#define PATH_LENGTH 20
using namespace std;
char sendBuff[BUF_SIZE];
char recvBuff[BUF_SIZE];
char fileName[PATH_LENGTH];
BOOL getFileTime(HANDLE hFile, LPSTR lpszCreationTime)//获取文件创建日期
{
FILETIME ftCreate, ftAccess, ftWrite;
SYSTEMTIME stUTC1, stLocal1;
// -------->获取 FileTime
if (!GetFileTime(hFile, &ftCreate, &ftAccess, &ftWrite)) {
cout << "error!" << endl;
return FALSE;
}
//---------> 转换: FileTime --> LocalTime
FileTimeToSystemTime(&ftCreate, &stUTC1);
SystemTimeToTzSpecificLocalTime(NULL, &stUTC1, &stLocal1);
// ---------> Show the date and time.
sprintf(lpszCreationTime, "%02d/%02d/%02d %02d:%02d",
stLocal1.wYear, stLocal1.wMonth, stLocal1.wDay,
stLocal1.wHour, stLocal1.wMinute);
return TRUE;
}
int main() {
WSADATA wsa;
if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0) {
cout << "Initialization failed." << endl;
return -1;
}
SOCKET client = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (client == -1) {
cout << "Socket failed." << endl;
return -1;
}
sockaddr_in sadr;
sadr.sin_family = AF_INET;
sadr.sin_port = htons(5000);
sadr.sin_addr.S_un.S_addr = inet_addr(SERVER_ID);
int nAddrlen = sizeof(sadr);
while (true) {
cout << "---------------------SENDING...---------------------" << endl;
cout << "Please input the filename: " << endl;
cin >> fileName;
FILE *fp;
if (!(fp = fopen(fileName, "rb"))) {
cout << "Fail to open file." << endl;
continue;
}
//先传送文件名
sendto(client, fileName, strlen(fileName), 0, (sockaddr*)&sadr, sizeof(sadr));
int length;
int ret;
while ((length = fread(sendBuff, 1, BUF_SIZE, fp)) > 0) {
ret = sendto(client, sendBuff, length, 0, (sockaddr*)&sadr, sizeof(sadr));
if (!ret) {
cout << "An error occurred while sending." << endl;
return -1;
}
ret = recvfrom(client, recvBuff, BUF_SIZE, 0, (sockaddr*)&sadr, &nAddrlen);
if (!ret) {
cout << "Fail to receive." << endl;
return -1;
}
else {
if (strcmp(recvBuff, "success")) {
cout << "Fail to receive." << endl;
return -1;
}
}
}
//传送文件发送结束信息
char end_flag[10] = "end";
ret = sendto(client, end_flag, length, 0, (sockaddr*)&sadr, sizeof(sadr));
//获取文件创建时间和大小
HANDLE hFile;
TCHAR szCreationTime[30];
hFile = CreateFile(fileName, 0, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
getFileTime(hFile, szCreationTime);
if (hFile == INVALID_HANDLE_VALUE) {
cout << "error!" << endl;
return -1;
}
int size = GetFileSize(hFile, NULL);
//传送时间和大小信息
ret = sendto(client, szCreationTime, 30, 0, (sockaddr*)&sadr, sizeof(sadr));
size = size / 1024 + 1;//B转KB
string tempSize = to_string(size);
tempSize += "KB";
char fileSize[20];
strcpy(fileSize, tempSize.c_str());
ret = sendto(client, fileSize, 20, 0, (sockaddr*)&sadr, sizeof(sadr));
cout << "successfully sent!" << endl;
fclose(fp);
CloseHandle(hFile);
}
closesocket(client);
WSACleanup();
return 0;
}
server.cpp:
/*
服务端程序
接收从客户端发送的文件，包含管理元数据（文件名、大小和日期）
*/
#include<iostream>
#include<WinSock2.h>
#include<winsock.h>
#pragma comment(lib,"ws2_32.lib")
#define BUF_SIZE 1024
#define PATH_LENGTH 20
using namespace std;
char sendBuff[BUF_SIZE];
char recvBuff[BUF_SIZE];
char fileName[PATH_LENGTH];
int main() {
WSADATA wsa;
if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0) {
cout << "Initialization failed." << endl;
return -1;
}
SOCKET server = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (server == -1) {
cout << "Socket failed." << endl;
return -1;
}
sockaddr_in my_addr, remote_addr;
int nAddrlen = sizeof(remote_addr);
my_addr.sin_family = AF_INET;
my_addr.sin_port = htons(5000);
my_addr.sin_addr.S_un.S_addr = INADDR_ANY;
if (::bind(server, (sockaddr*)&my_addr, sizeof(my_addr)) == SOCKET_ERROR) {
cout << "Bind error!" << endl;
return -1;
}
while (true) {
cout << "---------------------RECEIVING...---------------------" << endl;
//接收文件名
int ret = recvfrom(server, fileName, BUF_SIZE, 0, (sockaddr*)&remote_addr, &nAddrlen);
cout << "Filename: " << fileName << endl;
errno_t err;
FILE *fp;
if ((err = fopen_s(&fp, fileName, "wb")) < 0) {
cout << "Create failed." << endl;
return -1;
}
int length;
while ((length = recvfrom(server, recvBuff, BUF_SIZE, 0, (sockaddr*)&remote_addr, &nAddrlen))) {
if (!strcmp(recvBuff, "end"))//接收结束信息
break;
if (length == 0) {
cout << "An error occurred while receiving." << endl;
return -1;
}
int ret = fwrite(recvBuff, 1, length, fp);
if (ret < length) {
cout << "Write failed." << endl;
return -1;
}
sendto(server, "success", sizeof("success") + 1, 0, (SOCKADDR*)&remote_addr, sizeof(remote_addr));
}
//接收文件创建日期、大小信息
char creationTime[30];
char fileSize[20];
recvfrom(server, creationTime, 30, 0, (sockaddr*)&remote_addr, &nAddrlen);
recvfrom(server, fileSize, 20, 0, (sockaddr*)&remote_addr, &nAddrlen);
cout << "Creation Time：" << creationTime << endl;
cout << "Size：" << fileSize << endl;
cout << "Successfully received!" << endl;
fclose(fp);
}
closesocket(server);
WSACleanup();
return 0;
}
