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FTPn" "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 servern" "please close the connection before connect to a new servern"); } } 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 errorn"); } } } bool ftpClient::connect2Host(const char* hostName) { //创建socket clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); if (clientSocket < 0) { printf("cannot create socketn"); return false; } else printf("successfully create socketn"); 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 hostn"); return false; } else { printf("successfully connect to the hostn"); return true; } } bool ftpClient::sendRequest(char* instruction) { int r = send(clientSocket, instruction, strlen(instruction) + 1, 0); if (r == SOCKET_ERROR) { printf("request failedn"); return false; } else { printf("request successn"); char opt[5]; int i = 0, j = 0; while (instruction[i] != ' '&&instruction[i] != '') { opt[i] = instruction[i]; i++; } opt[i] = ''; i++; while (instruction[i] != '') { name[j] = instruction[i]; i++, j++; } name[j] = ''; if (strcmp(opt, "get") == 0) { if (getFile()) { printf("successfully downloadn"); } else printf("download failedn"); } else if (strcmp(opt, "put") == 0) { if (putFile()) { printf("successfully uploadn"); } else printf("upload failedn"); } else if (strcmp(opt, "pwd") == 0) { if (!getWorkDir()) printf("get work directory failedn"); } else if (strcmp(opt, "cd") == 0) { printf("operation finishedn"); } else { printf("syntex errorn"); 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 filen"); 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 filen"); 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("getWorkDirn"); 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 socketn"); return false; } else printf("successfully create socketn"); 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 errorn"); return false; } else printf("successfully bindn"); //监听 int l = listen(serverSocket, QUEUE_SIZE); if (l < 0) { printf("listen failedn"); return false; } else printf("successfully listenn"); 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 failedn"); } else { printf("successfully connectn"); while (1) { memset(buffer, 0, sizeof(buffer)); int ret; ret = recv(clientSocket, buffer, BUFFER_SIZE, 0); if (ret == SOCKET_ERROR) { printf("receive failedn"); } else { char opt[50]; printf("successfully receiven"); int i = 0, j = 0; printf("buffer = %sn", buffer); while (buffer[i] != ' '&&buffer[i] != '') { opt[i] = buffer[i]; i++; } opt[i] = ''; if (buffer[i] != '') { i++; } while (buffer[i] != '') { name[j] = buffer[i]; i++, j++; } name[j] = ''; 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 errorn"); } } } } } 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 filen"); 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 failedn"); return false; } else { printf("send successn"); } 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 failedn"); return false; } else { printf("send successn"); } } 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 failedn"); return false; } else { printf("successfully receiven"); } int size = atoi(length); std::ofstream out; out.open(path, std::ios::binary); if (!out) { printf("cannot save the filen"); 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 failedn"); break; } else { printf("successfully receiven"); 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 filen"); 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 failedn"); return false; } else { printf("send successn"); } 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 = %dn", total_size); r = send(clientSocket, buffer, size, 0); sp -= size; if (r == SOCKET_ERROR) { printf("send failedn"); return false; } else { printf("send successn"); } } 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] != ''; ++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] = ''; 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(); }

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