Socket网络编程--FTP客户端(2)(Windows)

　　上一篇FTP客户端讲到如果制作一个简单的FTP客户端，功能实现了，但是后面我们发现了问题，就是FTP是使用明文进行操作的。对于普通情况来说就无所谓了。但有时候要安全的一点的话，就应该使用FTP的安全版本。有SFTP和FTPs，两者都是FTP的安全版本，但是两者的实现原理差别还是很大的，具体自己搜索了解。

0.环境安装

　　环境使用我的这一篇文章安装好libssh2库。

　　http://www.cnblogs.com/wunaozai/p/4528394.html

　　使用一个带有SFTP功能的FTP服务器。注意有些FTP服务器是不带SFTP功能的。这里我使用这个FreeSSHd作为SFTP服务器。

　　http://www.freesshd.com/?ctt=download

　　关于freesshd配置说两句，Server status标签点击确定SSH server is running。SSH标签，确定配置完成。Authentication标签下Password authentication为Allowed，Public key authentication为Disabled，这样做的原因是我接下来要做的程序只支持密码登录，减少不必要的干扰，如果有需要，可以自己设定。Tunneling标签，所有选项选中，如果没有选中，本地如果网络复杂的话，可能会有问题。SFTP标签，选择一个作为FTP的根目录。Users标签，增加一个用户。基本设置就这些了。

1.示例讲解

　　我们先从libssh2中的示例程序进行讲解，libssh2源代码中的example文件夹中有几个常见的示例程序，我们此次先讲解上传文件和下载文件这两个基础功能。

　　下面这个是sftp_write_nonblock.c的源代码，已被折叠。

  1 /*
  2  * Sample showing how to do SFTP non-blocking write transfers.
  3  *
  4  * The sample code has default values for host name, user name, password
  5  * and path to copy, but you can specify them on the command line like:
  6  *
  7  * "sftp 192.168.0.1 user password sftp_write_nonblock.c /tmp/sftp_write_nonblock.c"
  8  */
  9 
 10 #include "libssh2_config.h"
 11 #include <libssh2.h>
 12 #include <libssh2_sftp.h>
 13 
 14 #ifdef HAVE_WINSOCK2_H
 15 # include <winsock2.h>
 16 #endif
 17 #ifdef HAVE_SYS_SOCKET_H
 18 # include <sys/socket.h>
 19 #endif
 20 #ifdef HAVE_NETINET_IN_H
 21 # include <netinet/in.h>
 22 #endif
 23 #ifdef HAVE_SYS_SELECT_H
 24 # include <sys/select.h>
 25 #endif
 26 # ifdef HAVE_UNISTD_H
 27 #include <unistd.h>
 28 #endif
 29 #ifdef HAVE_ARPA_INET_H
 30 # include <arpa/inet.h>
 31 #endif
 32 #ifdef HAVE_SYS_TIME_H
 33 # include <sys/time.h>
 34 #endif
 35 
 36 #include <sys/types.h>
 37 #include <fcntl.h>
 38 #include <errno.h>
 39 #include <stdio.h>
 40 #include <ctype.h>
 41 #include <time.h>
 42 
 43 static int waitsocket(int socket_fd, LIBSSH2_SESSION *session)
 44 {
 45     struct timeval timeout;
 46     int rc;
 47     fd_set fd;
 48     fd_set *writefd = NULL;
 49     fd_set *readfd = NULL;
 50     int dir;
 51 
 52     timeout.tv_sec = 10;
 53     timeout.tv_usec = 0;
 54 
 55     FD_ZERO(&fd);
 56 
 57     FD_SET(socket_fd, &fd);
 58 
 59     /* now make sure we wait in the correct direction */
 60     dir = libssh2_session_block_directions(session);
 61 
 62     if(dir & LIBSSH2_SESSION_BLOCK_INBOUND)
 63         readfd = &fd;
 64 
 65     if(dir & LIBSSH2_SESSION_BLOCK_OUTBOUND)
 66         writefd = &fd;
 67 
 68     rc = select(socket_fd + 1, readfd, writefd, NULL, &timeout);
 69 
 70     return rc;
 71 }
 72 
 73 int main(int argc, char *argv[])
 74 {
 75     unsigned long hostaddr;
 76     int sock, i, auth_pw = 1;
 77     struct sockaddr_in sin;
 78     const char *fingerprint;
 79     LIBSSH2_SESSION *session;
 80     const char *username="username";
 81     const char *password="password";
 82     const char *loclfile="sftp_write_nonblock.c";
 83     const char *sftppath="/tmp/sftp_write_nonblock.c";
 84     int rc;
 85     FILE *local;
 86     LIBSSH2_SFTP *sftp_session;
 87     LIBSSH2_SFTP_HANDLE *sftp_handle;
 88     char mem[1024 * 100];
 89     size_t nread;
 90     char *ptr;
 91     time_t start;
 92     long total = 0;
 93     int duration;
 94 
 95 #ifdef WIN32
 96     WSADATA wsadata;
 97     int err;
 98 
 99     err = WSAStartup(MAKEWORD(2,0), &wsadata);
100     if (err != 0) {
101         fprintf(stderr, "WSAStartup failed with error: %d
", err);
102         return 1;
103     }
104 #endif
105 
106     if (argc > 1) {
107         hostaddr = inet_addr(argv[1]);
108     } else {
109         hostaddr = htonl(0x7F000001);
110     }
111 
112     if (argc > 2) {
113         username = argv[2];
114     }
115     if (argc > 3) {
116         password = argv[3];
117     }
118     if (argc > 4) {
119         loclfile = argv[4];
120     }
121     if (argc > 5) {
122         sftppath = argv[5];
123     }
124 
125     rc = libssh2_init (0);
126     if (rc != 0) {
127         fprintf (stderr, "libssh2 initialization failed (%d)
", rc);
128         return 1;
129     }
130 
131     local = fopen(loclfile, "rb");
132     if (!local) {
133         fprintf(stderr, "Can't open local file %s
", loclfile);
134         return -1;
135     }
136 
137     /*
138      * The application code is responsible for creating the socket
139      * and establishing the connection
140      */
141     sock = socket(AF_INET, SOCK_STREAM, 0);
142 
143     sin.sin_family = AF_INET;
144     sin.sin_port = htons(22);
145     sin.sin_addr.s_addr = hostaddr;
146     if (connect(sock, (struct sockaddr*)(&sin),
147                 sizeof(struct sockaddr_in)) != 0) {
148         fprintf(stderr, "failed to connect!
");
149         return -1;
150     }
151 
152     /* Create a session instance */
153     session = libssh2_session_init();
154     if (!session)
155         return -1;
156 
157     /* Since we have set non-blocking, tell libssh2 we are non-blocking */
158     libssh2_session_set_blocking(session, 0);
159 
160     /* ... start it up. This will trade welcome banners, exchange keys,
161         * and setup crypto, compression, and MAC layers
162         */
163     while ((rc = libssh2_session_handshake(session, sock))
164            == LIBSSH2_ERROR_EAGAIN);
165     if (rc) {
166         fprintf(stderr, "Failure establishing SSH session: %d
", rc);
167         return -1;
168     }
169 
170     /* At this point we havn't yet authenticated.  The first thing to do is
171      * check the hostkey's fingerprint against our known hosts Your app may
172      * have it hard coded, may go to a file, may present it to the user,
173      * that's your call
174      */
175     fingerprint = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1);
176     fprintf(stderr, "Fingerprint: ");
177     for(i = 0; i < 20; i++) {
178         fprintf(stderr, "%02X ", (unsigned char)fingerprint[i]);
179     }
180     fprintf(stderr, "
");
181 
182     if (auth_pw) {
183         /* We could authenticate via password */
184         while ((rc = libssh2_userauth_password(session, username, password)) ==
185                LIBSSH2_ERROR_EAGAIN);
186         if (rc) {
187             fprintf(stderr, "Authentication by password failed.
");
188             goto shutdown;
189         }
190     } else {
191         /* Or by public key */
192         while ((rc = libssh2_userauth_publickey_fromfile(session, username,
193                                                          "/home/username/.ssh/id_rsa.pub",
194                                                          "/home/username/.ssh/id_rsa",
195                                                          password)) ==
196                LIBSSH2_ERROR_EAGAIN);
197     if (rc) {
198             fprintf(stderr, "	Authentication by public key failed
");
199             goto shutdown;
200         }
201     }
202 
203     fprintf(stderr, "libssh2_sftp_init()!
");
204     do {
205         sftp_session = libssh2_sftp_init(session);
206 
207         if (!sftp_session &&
208             (libssh2_session_last_errno(session) != LIBSSH2_ERROR_EAGAIN)) {
209             fprintf(stderr, "Unable to init SFTP session
");
210             goto shutdown;
211         }
212     } while (!sftp_session);
213 
214     fprintf(stderr, "libssh2_sftp_open()!
");
215     /* Request a file via SFTP */
216     do {
217         sftp_handle =
218         libssh2_sftp_open(sftp_session, sftppath,
219                           LIBSSH2_FXF_WRITE|LIBSSH2_FXF_CREAT|LIBSSH2_FXF_TRUNC,
220                           LIBSSH2_SFTP_S_IRUSR|LIBSSH2_SFTP_S_IWUSR|
221                           LIBSSH2_SFTP_S_IRGRP|LIBSSH2_SFTP_S_IROTH);
222 
223         if (!sftp_handle &&
224             (libssh2_session_last_errno(session) != LIBSSH2_ERROR_EAGAIN)) {
225             fprintf(stderr, "Unable to open file with SFTP
");
226             goto shutdown;
227         }
228     } while (!sftp_handle);
229 
230     fprintf(stderr, "libssh2_sftp_open() is done, now send data!
");
231 
232     start = time(NULL);
233 
234     do {
235         nread = fread(mem, 1, sizeof(mem), local);
236         if (nread <= 0) {
237             /* end of file */
238             break;
239         }
240         ptr = mem;
241 
242         total += nread;
243 
244         do {
245             /* write data in a loop until we block */
246             while ((rc = libssh2_sftp_write(sftp_handle, ptr, nread)) ==
247                    LIBSSH2_ERROR_EAGAIN) {
248                 waitsocket(sock, session);
249             }
250             if(rc < 0)
251                 break;
252             ptr += rc;
253             nread -= rc;
254 
255         } while (nread);
256     } while (rc > 0);
257 
258     duration = (int)(time(NULL)-start);
259 
260     fprintf(stderr, "%ld bytes in %d seconds makes %.1f bytes/sec
",
261            total, duration, total/(double)duration);
262 
263 
264     fclose(local);
265     libssh2_sftp_close(sftp_handle);
266     libssh2_sftp_shutdown(sftp_session);
267 
268 shutdown:
269 
270     while (libssh2_session_disconnect(session, "Normal Shutdown, Thank you for playing")
271            == LIBSSH2_ERROR_EAGAIN);
272     libssh2_session_free(session);
273 
274 #ifdef WIN32
275     closesocket(sock);
276 #else
277     close(sock);
278 #endif
279     fprintf(stderr, "all done
");
280 
281     libssh2_exit();
282 
283     return 0;
284 }

View Code

　　下面这个是sftp_nonblock.c的源代码

  1 /*
  2  * Sample showing how to do SFTP non-blocking transfers.
  3  *
  4  * The sample code has default values for host name, user name, password
  5  * and path to copy, but you can specify them on the command line like:
  6  *
  7  * "sftp_nonblock 192.168.0.1 user password /tmp/secrets"
  8  */
  9 
 10 #include "libssh2_config.h"
 11 #include <libssh2.h>
 12 #include <libssh2_sftp.h>
 13 
 14 #ifdef HAVE_WINSOCK2_H
 15 # include <winsock2.h>
 16 #endif
 17 #ifdef HAVE_SYS_SOCKET_H
 18 # include <sys/socket.h>
 19 #endif
 20 #ifdef HAVE_NETINET_IN_H
 21 # include <netinet/in.h>
 22 #endif
 23 #ifdef HAVE_SYS_SELECT_H
 24 # include <sys/select.h>
 25 #endif
 26 # ifdef HAVE_UNISTD_H
 27 #include <unistd.h>
 28 #endif
 29 #ifdef HAVE_ARPA_INET_H
 30 # include <arpa/inet.h>
 31 #endif
 32 #ifdef HAVE_SYS_TIME_H
 33 # include <sys/time.h>
 34 #endif
 35 
 36 #include <sys/types.h>
 37 #include <fcntl.h>
 38 #include <errno.h>
 39 #include <stdio.h>
 40 #include <ctype.h>
 41 
 42 /* diff in ms */
 43 static long tvdiff(struct timeval newer, struct timeval older)
 44 {
 45   return (newer.tv_sec-older.tv_sec)*1000+
 46       (newer.tv_usec-older.tv_usec)/1000;
 47 }
 48 
 49 static int waitsocket(int socket_fd, LIBSSH2_SESSION *session)
 50 {
 51     struct timeval timeout;
 52     int rc;
 53     fd_set fd;
 54     fd_set *writefd = NULL;
 55     fd_set *readfd = NULL;
 56     int dir;
 57 
 58     timeout.tv_sec = 10;
 59     timeout.tv_usec = 0;
 60 
 61     FD_ZERO(&fd);
 62 
 63     FD_SET(socket_fd, &fd);
 64 
 65     /* now make sure we wait in the correct direction */
 66     dir = libssh2_session_block_directions(session);
 67 
 68     if(dir & LIBSSH2_SESSION_BLOCK_INBOUND)
 69         readfd = &fd;
 70 
 71     if(dir & LIBSSH2_SESSION_BLOCK_OUTBOUND)
 72         writefd = &fd;
 73 
 74     rc = select(socket_fd + 1, readfd, writefd, NULL, &timeout);
 75 
 76     return rc;
 77 }
 78 
 79 int main(int argc, char *argv[])
 80 {
 81     unsigned long hostaddr;
 82     int sock, i, auth_pw = 1;
 83     struct sockaddr_in sin;
 84     const char *fingerprint;
 85     LIBSSH2_SESSION *session;
 86     const char *username="username";
 87     const char *password="password";
 88     const char *sftppath="/tmp/TEST";
 89     struct timeval start;
 90     struct timeval end;
 91     int rc;
 92     int total = 0;
 93     long time_ms;
 94     int spin = 0;
 95     LIBSSH2_SFTP *sftp_session;
 96     LIBSSH2_SFTP_HANDLE *sftp_handle;
 97 
 98 #ifdef WIN32
 99     WSADATA wsadata;
100     int err;
101 
102     err = WSAStartup(MAKEWORD(2,0), &wsadata);
103     if (err != 0) {
104         fprintf(stderr, "WSAStartup failed with error: %d
", err);
105         return 1;
106     }
107 #endif
108 
109     if (argc > 1) {
110         hostaddr = inet_addr(argv[1]);
111     } else {
112         hostaddr = htonl(0x7F000001);
113     }
114 
115     if (argc > 2) {
116         username = argv[2];
117     }
118     if (argc > 3) {
119         password = argv[3];
120     }
121     if (argc > 4) {
122         sftppath = argv[4];
123     }
124 
125     rc = libssh2_init (0);
126     if (rc != 0) {
127         fprintf (stderr, "libssh2 initialization failed (%d)
", rc);
128         return 1;
129     }
130 
131     /*
132      * The application code is responsible for creating the socket
133      * and establishing the connection
134      */
135     sock = socket(AF_INET, SOCK_STREAM, 0);
136 
137     sin.sin_family = AF_INET;
138     sin.sin_port = htons(22);
139     sin.sin_addr.s_addr = hostaddr;
140     if (connect(sock, (struct sockaddr*)(&sin),
141                 sizeof(struct sockaddr_in)) != 0) {
142         fprintf(stderr, "failed to connect!
");
143         return -1;
144     }
145 
146     /* Create a session instance */
147     session = libssh2_session_init();
148     if (!session)
149         return -1;
150 
151     /* Since we have set non-blocking, tell libssh2 we are non-blocking */
152     libssh2_session_set_blocking(session, 0);
153 
154     gettimeofday(&start, NULL);
155 
156     /* ... start it up. This will trade welcome banners, exchange keys,
157         * and setup crypto, compression, and MAC layers
158         */
159     while ((rc = libssh2_session_handshake(session, sock)) ==
160            LIBSSH2_ERROR_EAGAIN);
161     if (rc) {
162         fprintf(stderr, "Failure establishing SSH session: %d
", rc);
163         return -1;
164     }
165 
166     /* At this point we havn't yet authenticated.  The first thing to do
167         * is check the hostkey's fingerprint against our known hosts Your app
168         * may have it hard coded, may go to a file, may present it to the
169         * user, that's your call
170         */
171     fingerprint = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1);
172     fprintf(stderr, "Fingerprint: ");
173     for(i = 0; i < 20; i++) {
174         fprintf(stderr, "%02X ", (unsigned char)fingerprint[i]);
175     }
176     fprintf(stderr, "
");
177 
178     if (auth_pw) {
179         /* We could authenticate via password */
180         while ((rc = libssh2_userauth_password(session, username, password))
181                == LIBSSH2_ERROR_EAGAIN);
182         if (rc) {
183             fprintf(stderr, "Authentication by password failed.
");
184             goto shutdown;
185         }
186     } else {
187         /* Or by public key */
188         while ((rc =
189                 libssh2_userauth_publickey_fromfile(session, username,
190                                                     "/home/username/"
191                                                     ".ssh/id_rsa.pub",
192                                                     "/home/username/"
193                                                     ".ssh/id_rsa",
194                                                     password)) ==
195                LIBSSH2_ERROR_EAGAIN);
196         if (rc) {
197             fprintf(stderr, "	Authentication by public key failed
");
198             goto shutdown;
199         }
200     }
201 #if 0
202     libssh2_trace(session, LIBSSH2_TRACE_CONN);
203 #endif
204     fprintf(stderr, "libssh2_sftp_init()!
");
205     do {
206         sftp_session = libssh2_sftp_init(session);
207 
208         if(!sftp_session) {
209             if(libssh2_session_last_errno(session) ==
210                LIBSSH2_ERROR_EAGAIN) {
211                 fprintf(stderr, "non-blocking init
");
212                 waitsocket(sock, session); /* now we wait */
213             }
214             else {
215                 fprintf(stderr, "Unable to init SFTP session
");
216                 goto shutdown;
217             }
218         }
219     } while (!sftp_session);
220 
221     fprintf(stderr, "libssh2_sftp_open()!
");
222     /* Request a file via SFTP */
223     do {
224         sftp_handle = libssh2_sftp_open(sftp_session, sftppath,
225                                         LIBSSH2_FXF_READ, 0);
226 
227         if (!sftp_handle) {
228             if (libssh2_session_last_errno(session) != LIBSSH2_ERROR_EAGAIN) {
229                 fprintf(stderr, "Unable to open file with SFTP
");
230                 goto shutdown;
231             }
232             else {
233                 fprintf(stderr, "non-blocking open
");
234                 waitsocket(sock, session); /* now we wait */
235             }
236         }
237     } while (!sftp_handle);
238 
239     fprintf(stderr, "libssh2_sftp_open() is done, now receive data!
");
240     do {
241         char mem[1024*24];
242 
243         /* loop until we fail */
244         while ((rc = libssh2_sftp_read(sftp_handle, mem,
245                                        sizeof(mem))) == LIBSSH2_ERROR_EAGAIN) {
246             spin++;
247             waitsocket(sock, session); /* now we wait */
248         }
249         if (rc > 0) {
250             total += rc;
251             write(1, mem, rc);
252         } else {
253             break;
254         }
255     } while (1);
256 
257     gettimeofday(&end, NULL);
258     time_ms = tvdiff(end, start);
259     fprintf(stderr, "Got %d bytes in %ld ms = %.1f bytes/sec spin: %d
", total,
260            time_ms, total/(time_ms/1000.0), spin );
261 
262     libssh2_sftp_close(sftp_handle);
263     libssh2_sftp_shutdown(sftp_session);
264 
265 shutdown:
266 
267     fprintf(stderr, "libssh2_session_disconnect
");
268     while (libssh2_session_disconnect(session,
269                                       "Normal Shutdown, Thank you") ==
270            LIBSSH2_ERROR_EAGAIN);
271     libssh2_session_free(session);
272 
273 #ifdef WIN32
274     closesocket(sock);
275 #else
276     close(sock);
277 #endif
278     fprintf(stderr, "all done
");
279 
280     libssh2_exit();
281 
282     return 0;
283 }

View Code

　　上面一个是发送文件到sftp服务器，下面是从sftp服务器获取文件。编译和运行结果如下图所示。

2.修改示例程序

　　软件提供的源代码是比较完整的，为了方便，对里面的功能进行修改。修改为符合本次使用的windows版本，仅支持密码访问。

　　sftp-write.c 用于把本地文件上传到sftp服务器中

  1 #include "libssh2_config.h"
  2 #include <libssh2.h>
  3 #include <libssh2_sftp.h>
  4 #include <winsock2.h>
  5 #include <unistd.h>
  6 #include <sys/time.h>
  7 #include <sys/types.h>
  8 #include <fcntl.h>
  9 #include <errno.h>
 10 #include <stdio.h>
 11 #include <ctype.h>
 12 
 13 #define PORT 22
 14 #define HOST "127.0.0.1"
 15 #define USER "user"
 16 #define PWD  "user"
 17 #define FILENAME "wunaozai.txt"
 18 #define LOCLFILE "wunaozai.txt"
 19 
 20 long tvdiff(struct timeval newer, struct timeval older);
 21 int waitsocket(int socket_fd, LIBSSH2_SESSION *session);
 22 
 23 int main(int argc,char *argv[])
 24 {
 25     int sock, i;
 26     struct sockaddr_in sin;
 27     const char *fingerprint;
 28     LIBSSH2_SESSION *session;
 29     LIBSSH2_SFTP *sftp_session;
 30     LIBSSH2_SFTP_HANDLE *sftp_handle;
 31     int rc;
 32     FILE *local;
 33     char mem[1024 * 100];
 34     size_t nread;
 35     char *ptr;
 36     time_t start;
 37     long total = 0;
 38     int duration;
 39     int ret=-1; //用于表示返回结果
 40     int err;
 41 
 42     WSADATA wsadata;
 43     err = WSAStartup(MAKEWORD(2,0), &wsadata);
 44     if (err != 0) {
 45         fprintf(stderr, "WSAStartup failed with error: %d
", err);
 46         return 1;
 47     }
 48 
 49     rc = libssh2_init (0);
 50     if (rc != 0) {
 51         fprintf (stderr, "libssh2 initialization failed (%d)
", rc);
 52         return 1;
 53     }
 54 
 55     local = fopen(LOCLFILE, "rb");
 56     if (!local) {
 57         fprintf(stderr, "Can't open local file %s
", LOCLFILE);
 58         return -1;
 59     }
 60 
 61     /*
 62      * The application code is responsible for creating the socket
 63      * and establishing the connection
 64      */
 65     sock = socket(AF_INET, SOCK_STREAM, 0);
 66 
 67     sin.sin_family = AF_INET;
 68     sin.sin_port = htons(PORT);
 69     sin.sin_addr.S_un.S_addr = inet_addr(HOST);
 70     if (connect(sock, (struct sockaddr*)(&sin), sizeof(struct sockaddr_in)) != 0) {
 71         fprintf(stderr, "failed to connect!
");
 72         return -1;
 73     }
 74 
 75     /* Create a session instance */
 76     session = libssh2_session_init();
 77     if (!session) return -1;
 78 
 79     /* Since we have set non-blocking, tell libssh2 we are non-blocking */
 80     libssh2_session_set_blocking(session, 0);
 81 
 82     /* ... start it up. This will trade welcome banners, exchange keys,
 83      * and setup crypto, compression, and MAC layers
 84      */
 85     while ((rc = libssh2_session_handshake(session, sock)) == LIBSSH2_ERROR_EAGAIN)
 86         ;
 87     if (rc) {
 88         fprintf(stderr, "Failure establishing SSH session: %d
", rc);
 89         return -1;
 90     }
 91 
 92     //到这里我们还没有权限访问，所以接下来要做的是检查hostkey's finger,然后知道我们验证方式
 93     fingerprint = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1);
 94     fprintf(stderr, "Fingerprint: ");
 95     for(i = 0; i < 20; i++) {
 96         fprintf(stderr, "%02X ", (unsigned char)fingerprint[i]);
 97     }
 98     fprintf(stderr, "
");
 99 
100     //只能使用密码验证
101     while ((rc = libssh2_userauth_password(session, USER, PWD)) == LIBSSH2_ERROR_EAGAIN)
102         ;
103     if (rc) {
104         fprintf(stderr, "Authentication by password failed.
");
105         goto shutdown;
106     }
107 
108     //fprintf(stderr, "libssh2_sftp_init()!
");
109     do {
110         sftp_session = libssh2_sftp_init(session);
111         if (!sftp_session && (libssh2_session_last_errno(session) != LIBSSH2_ERROR_EAGAIN)) {
112             fprintf(stderr, "Unable to init SFTP session
");
113             goto shutdown;
114         }
115     } while (!sftp_session);
116     //fprintf(stderr, "libssh2_sftp_open()!
");
117 
118 
119     //请求一个文件，通过ssh2方式
120     do {
121         sftp_handle =
122             libssh2_sftp_open(sftp_session, FILENAME, LIBSSH2_FXF_WRITE|LIBSSH2_FXF_CREAT|LIBSSH2_FXF_TRUNC,
123                     LIBSSH2_SFTP_S_IRUSR|LIBSSH2_SFTP_S_IWUSR|
124                     LIBSSH2_SFTP_S_IRGRP|LIBSSH2_SFTP_S_IROTH);
125 
126         if (!sftp_handle && (libssh2_session_last_errno(session) != LIBSSH2_ERROR_EAGAIN)) {
127             fprintf(stderr, "Unable to open file with SFTP
"); //可能是没有写入权限，或者没有对应的目录
128             goto shutdown;
129         }
130     } while (!sftp_handle);
131 
132     fprintf(stderr, "libssh2_sftp_open() is done, now send data!
");
133 
134     start = time(NULL);
135 
136     do {
137         nread = fread(mem, 1, sizeof(mem), local);
138         if (nread <= 0) { //文件结束
139             break;
140         }
141         ptr = mem;
142         total += nread;
143         do {
144             //持续写入文件
145             while ((rc = libssh2_sftp_write(sftp_handle, ptr, nread)) == LIBSSH2_ERROR_EAGAIN) {
146                 waitsocket(sock, session);
147             }
148             if(rc < 0)
149                 break;
150             ptr += rc;
151             nread -= rc;
152         } while (nread);
153     } while (rc > 0);
154 
155     duration = (int)(time(NULL)-start);
156 
157     fprintf(stderr, "%ldK bytes in %d seconds makes %.1fK bytes/sec
", total/1024, duration+1, total/((double)duration+1)/1024);
158 
159 
160     fclose(local);
161     libssh2_sftp_close(sftp_handle);
162     libssh2_sftp_shutdown(sftp_session);
163 
164     ret = 0; //如果执行到这一步，那么表示成功上传文件到服务器
165 shutdown:
166 
167     while (libssh2_session_disconnect(session, "Normal Shutdown, Thank you for playing") == LIBSSH2_ERROR_EAGAIN)
168         ;
169     libssh2_session_free(session);
170     closesocket(sock);
171     fprintf(stderr, "all done
");
172     libssh2_exit();
173 
174     return ret;
175 }
176 
177 int waitsocket(int socket_fd, LIBSSH2_SESSION *session)
178 {
179     struct timeval timeout;
180     int rc;
181     fd_set fd;
182     fd_set *writefd = NULL;
183     fd_set *readfd = NULL;
184     int dir;
185 
186     timeout.tv_sec = 10;
187     timeout.tv_usec = 0;
188 
189     FD_ZERO(&fd);
190 
191     FD_SET(socket_fd, &fd);
192 
193     /* now make sure we wait in the correct direction */
194     dir = libssh2_session_block_directions(session);
195 
196     if(dir & LIBSSH2_SESSION_BLOCK_INBOUND)
197         readfd = &fd;
198 
199     if(dir & LIBSSH2_SESSION_BLOCK_OUTBOUND)
200         writefd = &fd;
201 
202     rc = select(socket_fd + 1, readfd, writefd, NULL, &timeout);
203     return rc;
204 }
205 /* diff in ms */
206 long tvdiff(struct timeval newer, struct timeval older)
207 {
208     return (newer.tv_sec-older.tv_sec)*1000+ (newer.tv_usec-older.tv_usec)/1000;
209 }

View Code

　　sftp-read.c 用于把服务器上的文件下载到本地中

  1 #include "libssh2_config.h"
  2 #include <libssh2.h>
  3 #include <libssh2_sftp.h>
  4 #include <winsock2.h>
  5 #include <unistd.h>
  6 #include <sys/time.h>
  7 #include <sys/types.h>
  8 #include <fcntl.h>
  9 #include <errno.h>
 10 #include <stdio.h>
 11 #include <ctype.h>
 12 
 13 #define PORT 22
 14 #define HOST "127.0.0.1"
 15 #define USER "user"
 16 #define PWD  "user"
 17 #define FILENAME "wunaozai.txt"
 18 #define LOCLFILE "wunaozai.txt"
 19 
 20 long tvdiff(struct timeval newer, struct timeval older);
 21 int waitsocket(int socket_fd, LIBSSH2_SESSION *session);
 22 
 23 
 24 int main(int argc, char *argv[])
 25 {
 26     int sock, i;
 27     struct sockaddr_in sin;
 28     const char *fingerprint;
 29     LIBSSH2_SESSION *session;
 30     LIBSSH2_SFTP *sftp_session;
 31     LIBSSH2_SFTP_HANDLE *sftp_handle;
 32     struct timeval start;
 33     struct timeval end;
 34     int total = 0;
 35     long time_ms;
 36     int spin = 0;
 37     int ret=0;
 38     int rc=1;
 39     FILE * fp;
 40 
 41     WSADATA wsadata;
 42     ret = WSAStartup(MAKEWORD(2,0), &wsadata);
 43     if (ret != 0) {
 44         fprintf(stderr, "WSAStartup failed with error: %d
", ret);
 45         return 1;
 46     }
 47 
 48     ret = libssh2_init (0);
 49     if (ret != 0) {
 50         fprintf (stderr, "libssh2 initialization failed (%d)
", ret);
 51         return 1;
 52     }
 53 
 54     sock = socket(AF_INET, SOCK_STREAM, 0);
 55     sin.sin_family = AF_INET;
 56     sin.sin_port = htons(PORT); //SFTP默认端口为22端口
 57     sin.sin_addr.S_un.S_addr = inet_addr(HOST);
 58     if (connect(sock, (struct sockaddr*)(&sin), sizeof(struct sockaddr_in)) != 0) {
 59         fprintf(stderr, "failed to connect!
");
 60         return -1;
 61     }
 62 
 63     session = libssh2_session_init(); //创建一个session
 64     if (!session) return -1;
 65 
 66     libssh2_session_set_blocking(session, 0); //设置为非阻塞方式
 67 
 68     while ((ret = libssh2_session_handshake(session, sock)) == LIBSSH2_ERROR_EAGAIN) //创建一个SSH session
 69         ;
 70 
 71     if (ret) {
 72         fprintf(stderr, "Failure establishing SSH session: %d
", ret);
 73         return -1;
 74     }
 75     //到这里我们还没有权限访问，所以接下来要做的是检查hostkey's finger
 76     fingerprint = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1);
 77     fprintf(stderr, "Fingerprint: ");
 78     for(i = 0; i < 20; i++) {
 79         fprintf(stderr, "%02X ", (unsigned char)fingerprint[i]);
 80     }
 81     fprintf(stderr, "
");
 82 
 83     //只是用密码进行验证
 84     while ((ret = libssh2_userauth_password(session, USER, PWD)) == LIBSSH2_ERROR_EAGAIN)
 85         ;
 86     if (ret) {
 87         fprintf(stderr, "Authentication by password failed.
");
 88         goto shutdown2;
 89     }
 90 
 91     fprintf(stderr, "libssh2_sftp_init()!
");
 92     do {
 93         sftp_session = libssh2_sftp_init(session);
 94         if(!sftp_session) {
 95             if(libssh2_session_last_errno(session) == LIBSSH2_ERROR_EAGAIN) {
 96                 fprintf(stderr, "non-blocking init
");
 97                 waitsocket(sock, session); /* now we wait */
 98             }
 99             else {
100                 fprintf(stderr, "Unable to init SFTP session
");
101                 goto shutdown2;
102             }
103         }
104     } while (!sftp_session);
105 
106     fprintf(stderr, "libssh2_sftp_open()!
");
107 
108     //请求一个文件，通过ssh方式
109     do {
110         sftp_handle = libssh2_sftp_open(sftp_session, FILENAME, LIBSSH2_FXF_READ, 0);
111 
112         if (!sftp_handle) {
113             if (libssh2_session_last_errno(session) != LIBSSH2_ERROR_EAGAIN) {
114                 fprintf(stderr, "Unable to open file with SFTP
");
115                 goto shutdown2;
116             }
117             else {
118                 fprintf(stderr, "non-blocking open
");
119                 waitsocket(sock, session); /* now we wait */
120             }
121         }
122     } while (!sftp_handle);
123 
124     gettimeofday(&start,NULL);
125     //打开文件进行保存
126     fp = fopen(LOCLFILE,"wb");
127     if(fp==NULL)
128     {
129         fprintf(stderr,"Can't open local file %s
",LOCLFILE);
130         return -1;
131     }
132     fprintf(stderr, "libssh2_sftp_open() is done, now receive data!
");
133     do {
134         char mem[1024*24];
135 
136         /* loop until we fail */
137         while ((ret = libssh2_sftp_read(sftp_handle, mem, sizeof(mem))) == LIBSSH2_ERROR_EAGAIN) {
138             spin++;
139             waitsocket(sock, session); /* now we wait */
140         }
141         if (ret > 0) {
142             total += ret;
143             //write(1, mem, ret);
144             fwrite(mem,1,ret,fp); //写入到文件中
145         } else {
146             break;
147         }
148     } while (1);
149     fclose(fp);
150     gettimeofday(&end,NULL);
151     time_ms = tvdiff(end, start);
152     //打印传输速率
153     fprintf(stderr, "Got %.4lf Mbytes in %.2lf sec = %.4lf Kbytes/sec spin: %d
", total/1024.0/1024.0,
154             time_ms/1000.0, total/((time_ms+1)/1000.0)/1024/1024, spin );
155 
156     libssh2_sftp_close(sftp_handle);
157     libssh2_sftp_shutdown(sftp_session);
158 
159     rc = 0;//执行到改行代码表示已经正常下载文件
160 
161 shutdown2:
162 
163     fprintf(stderr, "libssh2_session_disconnect
");
164     while (libssh2_session_disconnect(session, "Normal Shutdown, Thank you") == LIBSSH2_ERROR_EAGAIN)
165         ;
166     libssh2_session_free(session);
167     closesocket(sock);
168     fprintf(stderr, "all done
");
169     libssh2_exit();
170 
171     return rc;
172 }
173 
174 long tvdiff(struct timeval newer, struct timeval older)
175 {
176     return (newer.tv_sec-older.tv_sec)*1000+(newer.tv_usec-older.tv_usec)/1000;
177 }
178 
179 int waitsocket(int socket_fd, LIBSSH2_SESSION *session)
180 {
181     struct timeval timeout;
182     int ret;
183     fd_set fd;
184     fd_set *writefd = NULL;
185     fd_set *readfd = NULL;
186     int dir;
187     timeout.tv_sec = 10;
188     timeout.tv_usec = 0;
189     FD_ZERO(&fd);
190     FD_SET(socket_fd, &fd);
191     /* now make sure we wait in the correct direction */
192     dir = libssh2_session_block_directions(session);
193     if(dir & LIBSSH2_SESSION_BLOCK_INBOUND)
194         readfd = &fd;
195     if(dir & LIBSSH2_SESSION_BLOCK_OUTBOUND)
196         writefd = &fd;
197     ret = select(socket_fd + 1, readfd, writefd, NULL, &timeout);
198     return ret;
199 }

View Code

　　至于用到的libssh2_config.h这个文件，没有的话可以在代码中注释掉.

　　下面这个是freesshd产生的日志中一部分

 1 05-28-2015 14:18:05 HOST localhost SSH connection attempt.
 2 05-28-2015 14:18:05 HOST localhost SSH user successfully logged on using password.
 3 05-28-2015 14:18:06 SFTP service granted to user user.
 4 05-28-2015 14:18:06 HOST localhost user is uploading wunaozai.txt (E:wunaozai.txt)
 5 05-28-2015 14:18:06 HOST localhost SSH user disconnected.
 6 05-28-2015 14:18:23 HOST localhost SSH connection attempt.
 7 05-28-2015 14:18:23 HOST localhost SSH user successfully logged on using password.
 8 05-28-2015 14:18:23 SFTP service granted to user user.
 9 05-28-2015 14:18:23 HOST localhost user is uploading wunaozai.txt (E:wunaozai.txt)
10 05-28-2015 14:18:23 HOST localhost SSH user disconnected.
11 05-28-2015 14:18:49 HOST localhost SSH connection attempt.
12 05-28-2015 14:18:49 HOST localhost SSH user successfully logged on using password.
13 05-28-2015 14:18:49 SFTP service granted to user user.
14 05-28-2015 14:18:49 HOST localhost user is uploading wunaozai.txt (E:wunaozai.txt)
15 05-28-2015 14:18:49 HOST localhost SSH user disconnected.
16 05-28-2015 14:18:55 HOST localhost SSH connection attempt.
17 05-28-2015 14:18:56 HOST localhost SSH user successfully logged on using password.
18 05-28-2015 14:18:56 SFTP service granted to user user.
19 05-28-2015 14:18:56 HOST localhost user is downloading wunaozai.txt (E:wunaozai.txt)
20 05-28-2015 14:18:56 HOST localhost SSH user disconnected.

　　有了上面这两个主要的功能，SFTP的客户端就基本功能实现了，至于mkdir和dir功能就参考里面的示例程序，基本都可以看懂。

3.使用putty连接freesshd

　　了解过SFTP原理之后，就知道，SFTP其实跟FTP没有多大的关系，其实就是一个使用SSH协议，然后进行会话，会话过程保存为文件，嗯，大概就是这个样子了。所以我们可以使用普通的ssh软件进行登录，拿到该SFTP服务器站点的SHELL。然后可以各种操作，看起来很危险的样子，所以不管用什么SFTP服务器在配置用户的时候要注意的。 putty工具里面还有个PSFTP.exe这个工具可以连接到SFTP服务器，没事的也可以玩玩看。

　　本文地址: http://www.cnblogs.com/wunaozai/p/4534302.html

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原文地址：https://www.cnblogs.com/wunaozai/p/4534302.html