Qt C++调用libssh2实现sftp传输文件

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1.重点说明

FTP、FTPS、SFTP不要混淆，我们这里是SFTP

1.1SFTP

• SFTP（SSH File Transfer Protocol，也称 Secret File Transfer Protocol）是一种安全的文件传输协议，一种通过网络传输文件的安全方法；它确保使用私有和安全的数据流来安全地传输数据。

1.2 FTPS

• FTPS是一种对常用的文件传输协议（FTP）添加传输层安全（TLS）和安全套接层（SSL）加密协议支持的扩展协议。FTPS不应与基于SSH的SSH文件传输协议或是Secure FTP协议相混淆。

1.3 FTP

• FTP（File Transfer Protocol，文件传输协议） 是 TCP/IP 协议组中的协议之一。FTP协议包括两个组成部分，其一为FTP服务器，其二为FTP客户端。其中FTP服务器用来存储文件，用户可以使用FTP客户端通过FTP协议访问位于FTP服务器上的资源。在开发网站的时候，通常利用FTP协议把网页或程序传到Web服务器上。此外，由于FTP传输效率非常高，在网络上传输大的文件时，一般也采用该协议。
• 默认情况下FTP协议使用TCP端口中的 20和21这两个端口，其中20用于传输数据，21用于传输控制信息。但是，是否使用20作为传输数据的端口与FTP使用的传输模式有关，如果采用主动模式，那么数据传输端口就是20；如果采用被动模式，则具体最终使用哪个端口要服务器端和客户端协商决定。

2.测试环境搭建

2.1 Xlight FTP工具

Xlight FTP服务器是非常容易使用的FTP服务器。 为了保证高性能，FTP服务器全部用C语言写成，服务器运行时占用很少的系统资源。它具有高效网络算法，在大量用户情况下, 可以充分利用FTP服务器带宽, 能够轻松处理数千用户的同时下载。

• 我们使用了Xlight FTP工具，具体安装和配置这里不提供！
  

3.简单说明libssh2编译

3.1 windows下编译成功后得到：

3.2 Linux下成功编译后得到：

3.3 cmake输出信息参考：

-- The following features have been enabled:* Static library, creating libssh2 static library* Shared library, creating libssh2 shared library (.so/.dll)* Crypto backend, OpenSSL-- The following OPTIONAL packages have been found:* OpenSSL* ZLIB-- The following features have been disabled:* Logging, Logging of execution with debug trace* Without deprecated APIs* Compression, using zlib for compression-- Configuring done (0.0s)
-- Generating done (0.1s)
-- Build files have been written to: 

4.直接上代码

/*** SFTP download by libssh2*/#include <fcntl.h>
#include <errno.h>
#include <stdio.h>#include <ctype.h>#ifdef Q_OS_LINUX
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#else
#include <winsock2.h>
#include <Windows.h>
#endif#include "sftp_get.h"using namespace std;SftpGet::SftpGet(): m_socket(0), m_sshSession(NULL), m_sftpSession(NULL)
{
}SftpGet::~SftpGet()
{
}int SftpGet::Connect(const char* host, int port, const char* username, const char* password)
{int rc = libssh2_init(0);if (rc != 0){snprintf(m_lastError, sizeof(m_lastError), "libssh2 initialization failed: %d", rc);return rc;}m_socket = socket(AF_INET, SOCK_STREAM, 0);sockaddr_in sin;sin.sin_family = AF_INET;sin.sin_port = htons(port);sin.sin_addr.s_addr = inet_addr(host);if (::connect(m_socket, (struct sockaddr*)(&sin), sizeof(struct sockaddr_in)) != 0){snprintf(m_lastError, sizeof(m_lastError), "failed to connect!");return -1;}// Create a session instancem_sshSession = libssh2_session_init();if(!m_sshSession){snprintf(m_lastError, sizeof(m_lastError), "libssh2_session_init failed!");return -1;}// Since we have set non-blocking, tell libssh2 we are blockinglibssh2_session_set_blocking(m_sshSession, 1);rc = libssh2_session_handshake(m_sshSession, m_socket);if (rc != 0){snprintf(m_lastError, sizeof(m_lastError), "Failure establishing SSH session: %d", rc);return rc;}// const char* fingerprint =libssh2_hostkey_hash(m_sshSession, LIBSSH2_HOSTKEY_HASH_SHA1);// check what authentication methods are availableconst char* userauthlist = libssh2_userauth_list(m_sshSession, username, strlen(username));if (strstr(userauthlist, "password") == NULL){snprintf(m_lastError, sizeof(m_lastError), "Authentication by password not supported");return 1;}// authenticate via passwordif (libssh2_userauth_password(m_sshSession, username, password)){snprintf(m_lastError, sizeof(m_lastError), "Authentication by password failed");return 2;}m_sftpSession = libssh2_sftp_init(m_sshSession);if (!m_sftpSession){snprintf(m_lastError, sizeof(m_lastError), "Unable to init SFTP session");return -1;}return 0;
}int SftpGet::SFtpRead(const char* remoteFile, char* data_buf, int* data_len)
{// Request a file via SFTPLIBSSH2_SFTP_HANDLE* sftpHandle = libssh2_sftp_open(m_sftpSession, remoteFile, LIBSSH2_FXF_READ, 0);if (!sftpHandle){snprintf(m_lastError, sizeof(m_lastError), "Unable to open file with SFTP: %ld\n",libssh2_sftp_last_error(m_sftpSession));return -1;}// libssh2_sftp_open() is done, now receive data!int len = 0;while(1){if (len < *data_len){int sz = libssh2_sftp_read(sftpHandle, data_buf + len, *data_len - len);if (sz > 0){len += sz;}else{break;}}else{snprintf(m_lastError, sizeof(m_lastError), "The data buffer is too small for the file data");return 1;}}*data_len = len;libssh2_sftp_close(sftpHandle);return 0;
}int SftpGet::Download(const char* remoteFile, const char* localPath)
{// Request a file via SFTPLIBSSH2_SFTP_HANDLE* sftpHandle = libssh2_sftp_open(m_sftpSession, remoteFile, LIBSSH2_FXF_READ, 0);if (!sftpHandle){snprintf(m_lastError, sizeof(m_lastError), "Unable to open file with SFTP: %ld\n",libssh2_sftp_last_error(m_sftpSession));return -1;}// libssh2_sftp_open() is done, now receive data!FILE* fp = fopen(localPath, "w");if (!fp){snprintf(m_lastError, sizeof(m_lastError), "Fail to create file: %s", localPath);return 2;}char buf[1024];while(1){int sz = libssh2_sftp_read(sftpHandle, buf, sizeof(buf));if (sz > 0){fwrite(buf, 1, sz, fp);}else{break;}}fclose(fp);libssh2_sftp_close(sftpHandle);return 0;
}void SftpGet::Close()
{if (m_sftpSession){libssh2_sftp_shutdown(m_sftpSession);m_sftpSession = NULL;}if (m_sshSession){libssh2_session_disconnect(m_sshSession, "Shutdown");libssh2_session_free(m_sshSession);m_sshSession = NULL;}if (m_socket){::close(m_socket);m_socket = 0;}libssh2_exit();
}string SftpGet::GetLastError()
{return m_lastError;
}

调用

// 测试从SFtp,上传、下载文件
int Upload2DownloadFile_SFtp()
{SftpGet fg;int ret = fg.Connect("127.0.0.1", 22, "root", "johnshao");if (ret){std:string errmsg = fg.GetLastError();qDebug() << errmsg.c_str();return -1;}int len = 1024 * 1024;char buf[len] = { 0 };ret = fg.SFtpRead("interview/binary_find.cpp", buf, &len);if (ret){std::string errmsg = fg.GetLastError();qDebug() << errmsg.c_str();return -1;}qDebug() << buf;ret = fg.Download("interview/binary_find.cpp", "binary_find.cpp");if (ret){std::string errmsg = fg.GetLastError();qDebug() << errmsg.c_str();return -1;}return 0;
}

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