C++ socket实现miniFTP
时间：2022-03-12 08:49:16 | 栏目：C代码 | 点击：次
本文实例为大家分享了C++ socket实现miniFTP的方法，供大家参考，具体内容如下
客户端：
服务端：
建立连接
连接使用 TCP 连接，服务器和客户端分别创建自己的套接字一端，服务器等待连接，客户端发起连接（并指定服务器 ip）。在两者端口号一致且不被占用的情况下，连接建立。
在整个过程中，服务器对每一个来访的客户端建立一个连接，在客户未请求与服务器断开时，该连接一直存在，用户可以不断向服务器发出请求。（持久性、流水线型连接 ）
客户端断开后，关闭客户端的套接字部分，服务器继续等待新的连接。服务器一次只能处理一个客户端的连接，不支持并发访问。
PDU 格式
由于 ftp 应当支持几乎任意类型文件，而几乎所有类型文件都能用二进制来解析，所以我们采用了二进制的格式来读取以及写入文件。在整个过程中，我们并不关心文件的具体内容，也无需在程序中解析文件，而是将其当作数据流看待。
受到缓存区大小的限制，我们无法一次性传输整个文件，所以我们将文件按缓存区大小拆分成数据包分批发送，我们可以将数据及时从缓存区写入文件，这样就让出了缓存区空间。数据包仅仅包含数据，不包含头部或尾部信息。
此外，接收文件时，recv()函数将会循环调用，因此，我们需要一个信号来通知什么时候发送完毕。
一个想法是发送终止信号，这是可行的，但更好的方法是在一开始发送文件总字节数，让接收方根据剩余字节大小判断什么时候接收完毕。因为在写入文件时，我们需要指定写入的字节数，尤其是在发来的数据流字节数不等于缓冲区大小时。写入字节数的错误会导致文件受损。
接收确认
我们知道 TCP 是可靠传输协议，它采取了一系列措施来保证传输不会出错。所以在使用 TCP 连接时，我们相信数据在链路层上没有出差错，它一定会成功发送到对方手上。但是在客户端接收服务器发来的文件的时候，我们仍然需要服务器发来确认信息。原因在于，虽然我们可以保证链路层不出错，但是我们无法保证应用层不出错。例如，客户端可能会给出错误的文件名，因为接收不到服务器发来的信息，所以会陷入空等状态。
ftpClient.h
#pragma
#include<winsock.h>
class ftpClient
{
private:
enum {
SERVER_PORT = 9999,
BUFFER_SIZE = 4096
};
sockaddr_in serverChannel;
char buffer[BUFFER_SIZE];
int serverSocket;
int clientSocket;
bool isConnect;
char name[50];
bool getFile();
bool putFile();
bool acknowledge();
bool sendRequest(char* instruction);
bool connect2Host(const char* hostName);
bool getWorkDir();
public:
ftpClient();
~ftpClient();
void start();
};
ftpClient.cpp
#define _CRT_SECURE_NO_WARNINGS
#include"ftpClient.h"
#include<cstdio>
#include<io.h>
#include<cstring>
#include<fstream>
ftpClient::ftpClient()
{
WORD wVersionRequested;
WSADATA wsaData;
int ret;
//WinSock初始化：
wVersionRequested = MAKEWORD(2, 2);//希望使用的WinSock DLL的版本
ret = WSAStartup(wVersionRequested, &wsaData);
if (ret != 0)
{
printf("WSAStartup() failed!\n");
}
//确认WinSock DLL支持版本2.2：
if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2)
{
WSACleanup();
printf("Invalid Winsock version!\n");
}
isConnect = false;
}
void ftpClient::start()
{
char c[100];
char d[100];
printf("这里是FTP客户端，您可以输入help查看操作方法,输入quit退出客户端\n");
while (1) {
scanf("%s", c);
if (strcmp(c, "help") == 0) {
printf("get [fileName] -- 下载文件\n"
"put [fileName] -- 上传文件\n"
"ftp [ip] -- 登录FTP\n"
"pwd -- 显示服务器当前工作文件夹\n"
"cd [dirName] -- 更改当前文件夹\n"
"close -- 关闭与当前ftp的连接\n"
"quit -- 退出客户端\n"
);
}
else if (strcmp(c, "get") == 0) {
scanf("%s", d);
strcat(c, " ");
strcat(c, d);
if (!isConnect) {
printf("you haven't connected to any server!\n");
}
else sendRequest(c);
}
else if (strcmp(c, "put") == 0) {
scanf("%s", d);
strcat(c, " ");
strcat(c, d);
if (!isConnect) {
printf("you haven't connected to any server!\n");
}
else sendRequest(c);
}
else if (strcmp(c, "ftp") == 0) {
scanf("%s", d);
if (!isConnect&&connect2Host(d)) {
isConnect = true;
}
else if(isConnect){
printf("you have already connected to server\n"
"please close the connection before connect to a new server\n");
}
}
else if (strcmp(c, "pwd") == 0) {
if (!isConnect) {
printf("you haven't connected to any server!\n");
}
else sendRequest(c);
}
else if (strcmp(c, "cd") == 0) {
scanf("%s", d);
strcat(c, " ");
strcat(c, d);
if (!isConnect) {
printf("you haven't connected to any server!\n");
}
else sendRequest(c);
}
else if (strcmp(c, "quit") == 0) {
if (isConnect) {
strcpy(c, "close");
isConnect = false;
send(clientSocket, c, strlen(c) + 1, 0);
closesocket(clientSocket);
}
break;
}
else if (strcmp(c, "close") == 0) {
if (isConnect) {
isConnect = false;
send(clientSocket, c, strlen(c) + 1, 0);
closesocket(clientSocket);
}
}
else {
printf("syntex error\n");
}
}
}
bool ftpClient::connect2Host(const char* hostName)
{
//创建socket
clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (clientSocket < 0) {
printf("cannot create socket\n");
return false;
}
else printf("successfully create socket\n");
memset(&serverChannel, 0, sizeof(serverChannel));//初始化为0
serverChannel.sin_family = AF_INET;//channel协议家族AF_INET
serverChannel.sin_addr.S_un.S_addr = inet_addr(hostName);//地址
serverChannel.sin_port = htons(SERVER_PORT);//服务器端口
//建立连接
serverSocket = connect(clientSocket, (sockaddr*)&serverChannel, sizeof(serverChannel));
if (serverSocket < 0) {
printf("cannot connect to the host\n");
return false;
}
else {
printf("successfully connect to the host\n");
return true;
}
}
bool ftpClient::sendRequest(char* instruction)
{
int r = send(clientSocket, instruction, strlen(instruction) + 1, 0);
if (r == SOCKET_ERROR) {
printf("request failed\n");
return false;
}
else {
printf("request success\n");
char opt[5];
int i = 0, j = 0;
while (instruction[i] != ' '&&instruction[i] != '\0') {
opt[i] = instruction[i];
i++;
}
opt[i] = '\0';
i++;
while (instruction[i] != '\0') {
name[j] = instruction[i];
i++, j++;
}
name[j] = '\0';
if (strcmp(opt, "get") == 0) {
if (getFile()) {
printf("successfully download\n");
}
else printf("download failed\n");
}
else if (strcmp(opt, "put") == 0) {
if (putFile()) {
printf("successfully upload\n");
}
else printf("upload failed\n");
}
else if (strcmp(opt, "pwd") == 0) {
if (!getWorkDir())
printf("get work directory failed\n");
}
else if (strcmp(opt, "cd") == 0) {
printf("operation finished\n");
}
else {
printf("syntex error\n");
return false;
}
return true;
}
}
bool ftpClient::getFile()
{
memset(buffer, 0, sizeof(buffer));
int ret;
char length[20];
ret = recv(clientSocket, length, sizeof(length), 0);
if (ret == SOCKET_ERROR) {
return false;
}
else if (strcmp(length, "NAK") == 0) {
return false;
}
int size = atoi(length);
std::ofstream out;
out.open(name, std::ios::binary);
if (!out) {
printf("cannot save the file\n");
return false;
}
while (size>0) {
ret = recv(clientSocket, buffer, BUFFER_SIZE, 0);
int s = size < BUFFER_SIZE ? size : BUFFER_SIZE;
if (ret == SOCKET_ERROR) {
out.close();
return false;
}
else if (strcmp(buffer, "NAK") == 0) {
out.close();
return false;
}
else {
out.write(buffer, s);
}
size -= BUFFER_SIZE;
}
out.close();
return acknowledge();
}
bool ftpClient::putFile()
{
std::ifstream in;
//打开文件
in.open(name, std::ios::binary);
if (!in) {
printf("cannot open the file\n");
return false;
}
memset(buffer, 0, sizeof(buffer));
//得到文件的字节数
in.seekg(0, std::ios_base::end);
int sp = in.tellg();
int total_size = 0;
int r;
char length[20];
sprintf(length, "%d", sp);
//发送字节
r = send(clientSocket, length, sizeof(length), 0);
if (r == SOCKET_ERROR) {
return false;
}
while (sp > 0) {
in.clear();
in.seekg(total_size, std::ios_base::beg);
memset(buffer, 0, sizeof(buffer));
//读取文件
in.read(buffer, sizeof(buffer));
int size = sp < BUFFER_SIZE ? sp : BUFFER_SIZE;
total_size += size;
//发送文件
r = send(clientSocket, buffer, size, 0);
sp -= size;
if (r == SOCKET_ERROR) {
in.close();
return false;
}
}
in.close();
}
bool ftpClient::getWorkDir() {
printf("getWorkDir\n");
memset(buffer, 0, sizeof(buffer));
int ret;
char length[20];
ret = recv(clientSocket, length, sizeof(length), 0);
if (ret == SOCKET_ERROR) {
return false;
}
int size = atoi(length);
while (size>0) {
ret = recv(clientSocket, buffer, BUFFER_SIZE, 0);
if (ret == SOCKET_ERROR) {
return false;
}
else {
printf("%s", buffer);
}
size -= BUFFER_SIZE;
}
return true;
}
bool ftpClient::acknowledge()
{
int ret = recv(clientSocket, buffer, BUFFER_SIZE, 0);
if (ret > 0) {
if (strcmp(buffer, "NAK") == 0)return false;
else if (strcmp(buffer, "ACK") == 0)return true;
}
}
ftpClient::~ftpClient()
{
if (isConnect) {
isConnect = false;
char c[6];
strcpy(c, "close");
send(clientSocket, c, strlen(c) + 1, 0);
closesocket(clientSocket);
}
}
main.cpp
#define _CRT_SECURE_NO_WARNINGS
#define _WINSOCK_DEPRECATED_NO_WARNINGS
#pragma(lib,"ws2_32.lib")
#include"ftpClient.h"
#include<stdio.h>
int main()
{
ftpClient a;
a.start();
return 0;
}
ftpServer.h
#pragma once
#include<winsock.h>
class ftpServer
{
private:
enum {
SERVER_PORT = 9999,
BUFFER_SIZE = 4096,
QUEUE_SIZE = 10
};
char buffer[BUFFER_SIZE];
sockaddr_in serverChannel;
char name[50];
char workDir[100]; //store like C:\Users MARK:字符串末没有斜线！！
int serverSocket; //socket
int clientSocket;
bool sendFile();
bool receiveFile();
bool doPwd();
bool doCd();
bool isValidPath(char* path);
public:
ftpServer();
bool start();//开启服务器
};
ftpServer.cpp
#define _CRT_SECURE_NO_WARNINGS
#include"ftpServer.h"
#include<cstdio>
#include<cstdlib>
#include<fstream>
#include<cstring>
ftpServer::ftpServer()
{
WORD wVersionRequested;
WSADATA wsaData;
int ret;
//WinSock初始化：
wVersionRequested = MAKEWORD(2, 2);//希望使用的WinSock DLL的版本
ret = WSAStartup(wVersionRequested, &wsaData);
if (ret != 0)
{
printf("WSAStartup() failed!\n");
}
//确认WinSock DLL支持版本2.2：
if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2)
{
WSACleanup();
printf("Invalid Winsock version!\n");
}
//workDir初始化为当前路径
system("cd > tempFile");
std::ifstream in("tempFile", std::ifstream::in);
in >> workDir;
in.close();
}
bool ftpServer::start()
{
int on = 1;
//初始化服务器
memset(&serverChannel, 0, sizeof(serverChannel));
serverChannel.sin_family = AF_INET;
serverChannel.sin_addr.s_addr = htonl(INADDR_ANY);
serverChannel.sin_port = htons(SERVER_PORT);
//创建套接字
this->serverSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (serverSocket < 0) {
printf("cannot create socket\n");
return false;
}
else printf("successfully create socket\n");
setsockopt(serverSocket, SOL_SOCKET, SO_REUSEADDR,
(char*)&on, sizeof(on));
//绑定
int b = bind(serverSocket, (sockaddr*)&serverChannel,
sizeof(serverChannel));
if (b < 0) {
printf("bind error\n");
return false;
}
else printf("successfully bind\n");
//监听
int l = listen(serverSocket, QUEUE_SIZE);
if (l < 0) {
printf("listen failed\n");
return false;
}
else printf("successfully listen\n");
int len = sizeof(serverChannel);
//服务器等待连接
while (1) {
printf("waiting for connection...\n");
//接受一个连接
clientSocket = accept(serverSocket, (sockaddr*)&serverChannel,
&len);
if (clientSocket < 0) {
printf("accept failed\n");
}
else {
printf("successfully connect\n");
while (1) {
memset(buffer, 0, sizeof(buffer));
int ret;
ret = recv(clientSocket, buffer, BUFFER_SIZE, 0);
if (ret == SOCKET_ERROR) {
printf("receive failed\n");
}
else {
char opt[50];
printf("successfully receive\n");
int i = 0, j = 0;
printf("buffer = %s\n", buffer);
while (buffer[i] != ' '&&buffer[i] != '\0') {
opt[i] = buffer[i];
i++;
}
opt[i] = '\0';
if (buffer[i] != '\0') {
i++;
}
while (buffer[i] != '\0') {
name[j] = buffer[i];
i++, j++;
}
name[j] = '\0';
if (strcmp(opt, "get") == 0) {
char ret[4];
if (!sendFile()) {
strcpy(ret, "NAK");
send(clientSocket, ret, sizeof(ret), 0);
}
else {
strcpy(ret, "ACK");
send(clientSocket, ret, sizeof(ret), 0);
}
}
else if (strcmp(opt, "put") == 0) {
receiveFile();
}
else if (strcmp(opt, "pwd") == 0) {
doPwd();
}
else if (strcmp(opt, "cd") == 0) {
doCd();
}
else if (strcmp(opt, "close") == 0) {
break;
}
else {
printf("syntex error\n");
}
}
}
}
}
return true;
}
bool ftpServer::sendFile()
{
std::ifstream in;
char path[100];
strcpy(path, workDir);
strcat(path, "\\");
strcat(path, name);
in.open(path, std::ios::binary);
if (!in) {
printf("cannot open the file\n");
return false;
}
memset(buffer, 0, sizeof(buffer));
in.seekg(0, std::ios_base::end);
int sp = in.tellg();
int total_size = 0;
int r;
char length[20];
sprintf(length, "%d", sp);
r = send(clientSocket, length, sizeof(length), 0);
if (r == SOCKET_ERROR) {
printf("send failed\n");
return false;
}
else {
printf("send success\n");
}
while (sp > 0) {
in.clear();
in.seekg(total_size, std::ios_base::beg);
memset(buffer, 0, sizeof(buffer));
in.read(buffer, sizeof(buffer));
int size = sp < BUFFER_SIZE ? sp : BUFFER_SIZE;
total_size += size;
r = send(clientSocket, buffer, size, 0);
sp -= size;
if (r == SOCKET_ERROR) {
printf("send failed\n");
return false;
}
else {
printf("send success\n");
}
}
in.close();
return true;
}
bool ftpServer::receiveFile()
{
char path[100];
strcpy(path, workDir);
strcat(path, "\\");
strcat(path, name);
memset(buffer, 0, sizeof(buffer));
int ret;
char length[20];
ret = recv(clientSocket, length, sizeof(length), 0);
if (ret == SOCKET_ERROR) {
printf("receive failed\n");
return false;
}
else {
printf("successfully receive\n");
}
int size = atoi(length);
std::ofstream out;
out.open(path, std::ios::binary);
if (!out) {
printf("cannot save the file\n");
return false;
}
while (size>0) {
int s = size < BUFFER_SIZE ? size : BUFFER_SIZE;
ret = recv(clientSocket, buffer, BUFFER_SIZE, 0);
if (ret == SOCKET_ERROR) {
printf("receive failed\n");
break;
}
else {
printf("successfully receive\n");
out.write(buffer, s);
}
size -= BUFFER_SIZE;
}
out.close();
return true;
}
bool ftpServer::doPwd() {
char temCMD[150];
memset(temCMD, 0, sizeof(temCMD));
strcat(temCMD, "echo ");
strcat(temCMD, workDir);
strcat(temCMD, " > tempFile");
system(temCMD);
memset(temCMD, 0, sizeof(temCMD));
strcat(temCMD, "dir /b ");
strcat(temCMD, workDir);
strcat(temCMD, " >> tempFile");
system(temCMD);
std::ifstream in("tempFile", std::fstream::in);
if (!in) {
printf("cannot open the file\n");
return false;
}
memset(buffer, 0, sizeof(buffer));
in.seekg(0, std::ios_base::end);
int sp = in.tellg();
int total_size = 0;
int r;
char length[20];
sprintf(length, "%d", sp);
r = send(clientSocket, length, sizeof(length), 0);
if (r == SOCKET_ERROR) {
printf("send failed\n");
return false;
}
else {
printf("send success\n");
}
while (sp > 0) {
in.clear();
in.seekg(total_size, std::ios_base::beg);
memset(buffer, 0, sizeof(buffer));
in.read(buffer, sizeof(buffer));
int size = sp < BUFFER_SIZE ? sp : BUFFER_SIZE;
total_size += size;
printf("transfer size = %d\n", total_size);
r = send(clientSocket, buffer, size, 0);
sp -= size;
if (r == SOCKET_ERROR) {
printf("send failed\n");
return false;
}
else {
printf("send success\n");
}
}
in.close();
return true;
}
bool ftpServer::isValidPath(char* path) {
char temCMD[100];
memset(temCMD, 0, sizeof(temCMD));
strcat(temCMD, "cd ");
strcat(temCMD, path);
int res = system(temCMD);
return res == 0;
}
bool ftpServer::doCd() {
for (int i = 0; name[i] != '\0'; ++i) {
if (name[i] == '/')
name[i] = '\\';
}
if (name[0] == '.'&&name[1] == '.') {
char temDir[100];
strcpy(temDir, workDir);
for (int i = sizeof(temDir); i >= 0; --i) {
if (temDir[i] == '\\') {
temDir[i] = '\0';
break;
}
}
strcat(temDir, name + 2);
if (isValidPath(temDir)) {
strcpy(workDir, temDir);
}
else {
return false;
}
}
else if (name[0] == '.'&&name[1] != '.') {
char temDir[100];
strcpy(temDir, workDir);
strcat(temDir, name + 1);
if (isValidPath(temDir)) {
strcpy(workDir, temDir);
}
else {
return false;
}
}
else if (name[1] == ':') {
if (isValidPath(name)) {
strcpy(workDir, name);
}
else {
return false;
}
}
else {
char temDir[100];
strcpy(temDir, workDir);
strcat(temDir, "\\");
strcat(temDir, name);
if (isValidPath(temDir)) {
strcpy(workDir, temDir);
}
else {
return false;
}
}
return true;
}
main.cpp
#include"ftpServer.h"
#pragma(lib,"ws2_32.lib")
int main()
{
ftpServer f;
f.start();
}