C++ socket实现miniFTP

发布时间：2020-12-16 05:16:48 所属栏目：百科来源：网络整理

导读：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

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","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","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,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,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,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,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,0); 
  if (r == SOCKET_ERROR) { 
    return false; 
  } 
  while (sp > 0) { 
    in.clear(); 
    in.seekg(total_size,std::ios_base::beg); 
    memset(buffer,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,size,0); 
 
    sp -= size; 
    if (r == SOCKET_ERROR) { 
      in.close(); 
      return false; 
    } 
  } 
  in.close(); 
} 
 
bool ftpClient::getWorkDir() { 
  printf("getWorkDirn"); 
  memset(buffer,0); 
  if (ret == SOCKET_ERROR) { 
    return false; 
  } 
  int size = atoi(length); 
  while (size>0) { 
    ret = recv(clientSocket,0); 
    if (ret == SOCKET_ERROR) { 
      return false; 
    } 
    else { 
      printf("%s",buffer); 
    } 
    size -= BUFFER_SIZE; 
  } 
  return true; 
} 
 
bool ftpClient::acknowledge() 
{ 
  int ret = recv(clientSocket,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,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,&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,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,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,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,&len); 
    if (clientSocket < 0) { 
      printf("accept failedn"); 
    } 
    else { 
      printf("successfully connectn"); 
      while (1) { 
        memset(buffer,sizeof(buffer)); 
        int ret; 
 
        ret = recv(clientSocket,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,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,sizeof(buffer)); 
  in.seekg(0,sp); 
   
  r = send(clientSocket,0); 
 
  if (r == SOCKET_ERROR) { 
    printf("send failedn"); 
    return false; 
  } 
  else { 
    printf("send successn"); 
  } 
 
  while (sp > 0) { 
    in.clear(); 
    in.seekg(total_size,sizeof(buffer)); 
    in.read(buffer,sizeof(buffer)); 
    int size = sp < BUFFER_SIZE ? sp : BUFFER_SIZE; 
    total_size += size; 
    r = send(clientSocket,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,name); 
  memset(buffer,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,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,sizeof(temCMD)); 
  strcat(temCMD,"echo "); 
  strcat(temCMD,workDir); 
  strcat(temCMD," > tempFile"); 
  system(temCMD); 
  memset(temCMD,"dir /b "); 
  strcat(temCMD," >> tempFile"); 
  system(temCMD); 
 
  std::ifstream in("tempFile",std::fstream::in); 
  if (!in) { 
    printf("cannot open the filen"); 
    return false; 
  } 
  memset(buffer,sp); 
  r = send(clientSocket,0); 
 
  if (r == SOCKET_ERROR) { 
    printf("send failedn"); 
    return false; 
  } 
  else { 
    printf("send successn"); 
  } 
  while (sp > 0) { 
    in.clear(); 
    in.seekg(total_size,sizeof(buffer)); 
    int size = sp < BUFFER_SIZE ? sp : BUFFER_SIZE; 
    total_size += size; 
    printf("transfer size = %dn",total_size); 
    r = send(clientSocket,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,"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,""); 
    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(); 
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持编程小技巧。

（编辑：李大同）

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