代理tcp服务器如何实现ftp功能？

[bravemanly]

大家好。
我现在在做一个tcp代理服务器，实现转发的功能。我有3台电脑，分别作为本地客户端，代理服务器以及远程客户端，其中代理服务器上面有2个网卡，一个
是内网的，一个是外网的。
本地客户机的ip：192.168.0.10

代理服务器的ip：
内网的ip:192.168.0.1
外网的ip:202.202.68.191


远程服务器的ip：202.202.68.201


最终就是想在本地客户机192.168.0.10的基础上通过cuteftp 登陆到远程主机202.202.68.201的ftp服务器上面，中间是
通过代理服务器实现转发的功能。


具体代码如下，现在能实现识别用户名和密码，但是在cuteftp上一直提示“数据socket建立失败”，请各位高人指点，这个代码该怎么修改和添加
才能实现ftp功能。在此先感谢了。

代码超过了帖子的长度，所以不能贴上来。
有兴趣的朋友，请留下邮箱，我把代码给发过去。
请高人指教。谢谢。

[bravemanly]

我把代码分部贴出来，请遇到过类似问题的高人修改一下，谢谢。
#include <ctype.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <signal.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <sys/file.h>
#include <fcntl.h>


#define TCP_PROTO "tcp"


int proxy_port; /* port to listen for proxy connections on */
struct sockaddr_in hostaddr; /* remote computer's address */


extern int errno; /* defined by libc.a */
/*extern char *sys_errlist[];*/


void parse_args (int argc, char **argv);
void daemonize (int servfd);
void do_proxy (int usersockfd);
void reap_status (void);
void errorout (char *msg);


/
***************************************************************************­*
function: main
description: Main level driver. After daemonizing the process, a
socket
is opened to listen for connections on the proxy port,
connections are accepted and children are spawned to handle
each new connection.
arguments:
argc,argv you know what those are.


return value: none.
calls: parse_args, do_proxy.
globals: reads proxy_port.
***************************************************************************­*/


main (argc,argv)
int argc;
char **argv;
{
int clilen;
int childpid;
int sockfd, newsockfd;
struct sockaddr_in servaddr, cliaddr;


parse_args(argc,argv);


/* prepare an address struct to listen for connections */
bzero((char *) &servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = proxy_port;


/* get a socket... */
if ((sockfd = socket(AF_INET,SOCK_STREAM,0)) < 0) {
fputs("failed to create server socket",stderr);
exit(1);
}


printf("Create socket successful!\n");


/* ...and bind our address and port to it */
if (bind(sockfd,(struct sockaddr *) (&servaddr),sizeof(servaddr))
< 0) {
fputs("faild to bind server socket to specified port",stderr);
exit(1);
}
printf("Bind host succeed!\n");


/* get ready to accept with at most 5 clients waiting to connect
*/
listen(sockfd,5);


printf("listening \n");


/* turn ourselves into a daemon */


daemonize(sockfd);


/* fall into a loop to accept new connections and spawn children
*/
while (1) {


/* accept the next connection */
clilen = sizeof(struct sockaddr_in);
newsockfd = accept(sockfd, (struct sockaddr *) (&cliaddr),
&clilen);


printf("Create new connection!\n");


if (newsockfd < 0 && errno == EINTR)
continue; /* a signal might interrupt our accept() call */
else if (newsockfd < 0)
/* something quite amiss -- kill the server */
errorout("failed to accept connection");


/* fork a child to handle this connection */
if ((childpid = fork()) == 0) {
close(sockfd);
do_proxy(newsockfd);
exit(0);
}


/* if fork() failed, the connection is silently dropped --
oops! */


close(newsockfd);
}



}

[bravemanly]

/
***************************************************************************­*
function: parse_args
description: parse the command line args.
arguments:
argc,argv you know what these are.

return value: none.
calls: none.
globals: writes proxy_port, writes hostaddr.
***************************************************************************­*/


void parse_args (argc,argv)
int argc;
char **argv;
{
int i;
struct hostent *hostp;
struct servent *servp;
unsigned long inaddr;
struct {
char proxy_port [16];
char isolated_host [64];
char service_name [32];
} pargs;


/*input is abnormal*/
if (argc < 4) {
printf("usage: %s <proxy-port> <remote host> <server-name|port-
number>\r\n",argv[0]);
exit(1);
}


strcpy(pargs.proxy_port,argv[1]);
strcpy(pargs.isolated_host,argv[2]);
strcpy(pargs.service_name,argv[3]);


for (i = 0; i < strlen(pargs.proxy_port); i++)
if (!isdigit(*(pargs.proxy_port + i))) break;


if (i == strlen(pargs.proxy_port))
proxy_port = htons(atoi(pargs.proxy_port));
else {
printf("%s: invalid proxy port",pargs.proxy_port);
exit(0);
}


bzero(&hostaddr,sizeof(hostaddr));
hostaddr.sin_family = AF_INET;
if ((inaddr = inet_addr(pargs.isolated_host)) != INADDR_NONE)
bcopy(&inaddr,&hostaddr.sin_addr,sizeof(inaddr));
else if ((hostp = gethostbyname(pargs.isolated_host)) != NULL)
bcopy(hostp->h_addr,&hostaddr.sin_addr,hostp->h_length);
else {
printf("%s: unknown host",pargs.isolated_host);
exit(1);
}


if ((servp = getservbyname(pargs.service_name,TCP_PROTO)) !=
NULL)
hostaddr.sin_port = servp->s_port;
else if (atoi(pargs.service_name) > 0)
hostaddr.sin_port = htons(atoi(pargs.service_name));
else {
printf("%s: invalid/unknown service name or port
number",pargs.service_name);
exit(1);
}



}


/
***************************************************************************­*
function: daemonize
description: detach the server process from the current context,
creating a pristine, predictable environment in which it
will execute.
arguments:
servfd file descriptor in use by server.

return value: none.
calls: none.
globals: none.
***************************************************************************­*/


void daemonize (servfd)
int servfd;
{
int childpid, fd, fdtablesize;


/* ignore terminal I/O, stop signals */
signal(SIGTTOU,SIG_IGN);
signal(SIGTTIN,SIG_IGN);
signal(SIGTSTP,SIG_IGN);


/* fork to put us in the background (whether or not the user
specified '&' on the command line */


if ((childpid = fork()) < 0) {
fputs("failed to fork first child",stderr);
exit(1);
}
else if (childpid > 0)
exit(0); /* terminate parent, continue in child */


setsid();


/* dissociate from process group */
/*
if (setpgrp(0,getpid()) < 0) {
fputs("failed to become process group leader",stderr);
exit(1);
}
*/


/* lose controlling terminal */
if ((fd = open("/dev/tty",O_RDWR)) >= 0) {
ioctl(fd,TIOCNOTTY,NULL);
close(fd);
}


/* close any open file descriptors */
for (fd = 0, fdtablesize = getdtablesize(); fd < fdtablesize; fd+
+)
if (fd != servfd) close(fd);


/* set working directory to / to allow filesystems to be
unmounted */
chdir("/");


/* clear the inherited umask */
umask(0);


/* setup zombie prevention */
/*
signal(SIGCLD,reap_status);
*/



}

[bravemanly]

/
***************************************************************************­*
function: parse_args
description: parse the command line args.
arguments:
argc,argv you know what these are.

return value: none.
calls: none.
globals: writes proxy_port, writes hostaddr.
***************************************************************************­*/


void parse_args (argc,argv)
int argc;
char **argv;
{
int i;
struct hostent *hostp;
struct servent *servp;
unsigned long inaddr;
struct {
char proxy_port [16];
char isolated_host [64];
char service_name [32];
} pargs;


/*input is abnormal*/
if (argc < 4) {
printf("usage: %s <proxy-port> <remote host> <server-name|port-
number>\r\n",argv[0]);
exit(1);
}


strcpy(pargs.proxy_port,argv[1]);
strcpy(pargs.isolated_host,argv[2]);
strcpy(pargs.service_name,argv[3]);


for (i = 0; i < strlen(pargs.proxy_port); i++)
if (!isdigit(*(pargs.proxy_port + i))) break;


if (i == strlen(pargs.proxy_port))
proxy_port = htons(atoi(pargs.proxy_port));
else {
printf("%s: invalid proxy port",pargs.proxy_port);
exit(0);
}


bzero(&hostaddr,sizeof(hostaddr));
hostaddr.sin_family = AF_INET;
if ((inaddr = inet_addr(pargs.isolated_host)) != INADDR_NONE)
bcopy(&inaddr,&hostaddr.sin_addr,sizeof(inaddr));
else if ((hostp = gethostbyname(pargs.isolated_host)) != NULL)
bcopy(hostp->h_addr,&hostaddr.sin_addr,hostp->h_length);
else {
printf("%s: unknown host",pargs.isolated_host);
exit(1);
}


if ((servp = getservbyname(pargs.service_name,TCP_PROTO)) !=
NULL)
hostaddr.sin_port = servp->s_port;
else if (atoi(pargs.service_name) > 0)
hostaddr.sin_port = htons(atoi(pargs.service_name));
else {
printf("%s: invalid/unknown service name or port
number",pargs.service_name);
exit(1);
}



}


/
***************************************************************************­*
function: daemonize
description: detach the server process from the current context,
creating a pristine, predictable environment in which it
will execute.
arguments:
servfd file descriptor in use by server.

return value: none.
calls: none.
globals: none.
***************************************************************************­*/


void daemonize (servfd)
int servfd;
{
int childpid, fd, fdtablesize;


/* ignore terminal I/O, stop signals */
signal(SIGTTOU,SIG_IGN);
signal(SIGTTIN,SIG_IGN);
signal(SIGTSTP,SIG_IGN);


/* fork to put us in the background (whether or not the user
specified '&' on the command line */


if ((childpid = fork()) < 0) {
fputs("failed to fork first child",stderr);
exit(1);
}
else if (childpid > 0)
exit(0); /* terminate parent, continue in child */


setsid();


/* dissociate from process group */
/*
if (setpgrp(0,getpid()) < 0) {
fputs("failed to become process group leader",stderr);
exit(1);
}
*/


/* lose controlling terminal */
if ((fd = open("/dev/tty",O_RDWR)) >= 0) {
ioctl(fd,TIOCNOTTY,NULL);
close(fd);
}


/* close any open file descriptors */
for (fd = 0, fdtablesize = getdtablesize(); fd < fdtablesize; fd+
+)
if (fd != servfd) close(fd);


/* set working directory to / to allow filesystems to be
unmounted */
chdir("/");


/* clear the inherited umask */
umask(0);


/* setup zombie prevention */
/*
signal(SIGCLD,reap_status);
*/



}

[帅得不敢出门]

友情up

[bravemanly]

***************************************************************************­*
function: do_proxy
description: does the actual work of virtually connecting a client to
the telnet service on the isolated host.
arguments:
usersockfd socket to which the client is connected.

return value: none.
calls: none.
globals: reads hostaddr.
***************************************************************************­*/


void do_proxy (usersockfd)
int usersockfd;
{
int isosockfd;
fd_set rdfdset;
int connstat;
int iolen;
char buf [2048];


/* open a socket to connect to the isolated host */
if ((isosockfd = socket(AF_INET,SOCK_STREAM,0)) < 0)
errorout("failed to create socket to host");


printf("Succeed in creating new socket!\n");
/* attempt a connection */
connstat = connect(isosockfd,(struct sockaddr *)
&hostaddr,sizeof(hostaddr));
printf("Attempt a connection.\n");


switch (connstat) {
case 0:
break;
case ETIMEDOUT:
case ECONNREFUSED:
case ENETUNREACH:
strcpy(buf,strerror(errno)); /* sys_errlist outdated, we use
use strerror function now.added by liaoy*/
strcat(buf,"\r\n");
write(usersockfd,buf,strlen(buf));
close(usersockfd);
exit(1); /* die peacefully if we can't establish a connection
*/
break;
default:
errorout("failed to connect to host");
}


/* now we're connected, serve fall into the data echo loop */
while (1) {
/* Select for readability on either of our two sockets */
FD_ZERO(&rdfdset);
FD_SET(usersockfd,&rdfdset);
FD_SET(isosockfd,&rdfdset);
if (select(FD_SETSIZE,&rdfdset,NULL,NULL,NULL) < 0)
errorout("select failed");


/* is the client sending data? */
if (FD_ISSET(usersockfd,&rdfdset)) {
if ((iolen = recv(usersockfd,buf,sizeof(buf),0)) <= 0)
break; /* zero length means the client disconnected */


send(isosockfd,buf,iolen,0);
printf("Client sends data :%s",buf);
}


/* is the host sending data? */
if (FD_ISSET(isosockfd,&rdfdset)) {
if ((iolen = recv(isosockfd,buf,sizeof(buf),0))<= 0)
break; /* zero length means the host disconnected */


send(usersockfd,buf,iolen,0);
printf("Host sends data: %s",buf);
}
}


/* we're done with the sockets */
close(isosockfd);
close(usersockfd);



}


/
***************************************************************************­*
function: errorout
description: displays an error message on the console and kills the
current process.
arguments:
msg message to be displayed.

return value: none -- does not return.
calls: none.
globals: none.
***************************************************************************­*/


void errorout (msg)
char *msg;
{
FILE *console;


console = fopen("/dev/console","a");
fprintf(console,"proxyd: %s",msg);
fclose(console);
exit(1);



}

[bravemanly]

在线等高人指点，我的qq是610258988，谢谢了

[沙漠里的海豚]

呵呵 帮忙up一下

[bravemanly]

高手们，请出一下手吧，谢谢了

[koo8]

帮忙顶起来，好长的代码，学习...

[青葱岁月不可追]

进来学习……

[jiajia330013]

用户名和密码能够实现功能，说明FTP的控制连接是没有问题的

LZ说的cuteftp提示建连失败，应该是FTP的数据连接出了问题了

我先看看你的代码

[bravemanly]

是数据socket没有连接起来，但是我搞不清楚，数据socket该怎么连接实现，请大侠们指点下，该在哪里添加并且怎么添加？