具体错误：
About to connect() to 9.186.12.115 port 990 (#0)
* Trying 9.186.12.115... connected
* Connected to 9.186.12.115 (9.186.12.115) port 990 (#0)
* FTP 0x29d5b2d0 state change from STOP to WAIT220
< 220 ProFTPD 1.3.0a Server (Curl Testing FTP Server ) [9.186.12.115]
> AUTH SSL
* FTP 0x29d5b2d0 state change from WAIT220 to AUTH
< 234 AUTH SSL successful
* successfully set certificate verify locations:
* CAfile: data/bin/ca102.crt
CApath: none
* SSLv2, Client hello (1):
} [data not shown]
* SSLv3, TLS handshake, Server hello (2):
{ [data not shown]
* SSLv3, TLS handshake, CERT (11):
{ [data not shown]
* SSLv3, TLS handshake, Server key exchange (12):
{ [data not shown]
* SSLv3, TLS handshake, Request CERT (13):
{ [data not shown]
* SSLv3, TLS handshake, Server finished (14):
{ [data not shown]
* SSLv3, TLS handshake, CERT (11):
} [data not shown]
* SSLv3, TLS handshake, Client key exchange (16):
} [data not shown]
* SSLv3, TLS handshake, CERT verify (15):
} [data not shown]
* SSLv3, TLS change cipher, Client hello (1):
} [data not shown]
* SSLv3, TLS handshake, Finished (20):
} [data not shown]
* SSLv3, TLS change cipher, Client hello (1):
{ [data not shown]
* SSLv3, TLS handshake, Finished (20):
{ [data not shown]
* SSL connection using DHE-RSA-AES256-SHA
* Server certificate:
* subject: /C=CH/ST=shanghai/L=shanghai/O=ibm/OU=cstl/CN=9.186.12.115/emailAddress=tufeng@cn.ibm.com
* start date: 2007-07-10 06:03:48 GMT
* expire date: 2017-07-07 06:03:48 GMT
* common name: 9.186.12.115 (matched)
* issuer: /C=CH/ST=shanghai/L=shanghai/O=ibm/OU=cstl/CN=9.186.12.115/emailAddress=tufeng@cn.ibm.com
* SSL certificate verify ok.
> USER ftptest
* FTP 0x29d5b2d0 state change from AUTH to USER
< 331 Password required for ftptest.
> PASS ftptest
* FTP 0x29d5b2d0 state change from USER to PASS
< 230 User ftptest logged in.
> PBSZ 0
* FTP 0x29d5b2d0 state change from PASS to PBSZ
< 200 PBSZ 0 successful
> PROT P
* FTP 0x29d5b2d0 state change from PBSZ to PROT
< 200 Protection set to Private
> PWD
* FTP 0x29d5b2d0 state change from PROT to PWD
< 257 "/" is current directory.
* Entry path is '/'
* FTP 0x29d5b2d0 state change from PWD to STOP
* protocol connect phase DONE
* DO phase starts
* Telling server to connect to 1.2.3.4:5904
> PORT 1,2,3,4,23,16
* FTP 0x29d5b2d0 state change from STOP to PORT
< 200 PORT command successful
* Connect data stream actively
* FTP 0x29d5b2d0 state change from PORT to STOP
* DO phase is complete
* DO-MORE phase starts
> TYPE A
* FTP 0x29d5b2d0 state change from STOP to LIST_TYPE
< 200 Type set to A
> LIST
* FTP 0x29d5b2d0 state change from LIST_TYPE to LIST
< 425 Unable to build data connection: Connection timed out
* RETR response: 425
* DO-MORE phase ends with 19
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- 0:03:22 --:--:-- 0* Connection #0 to host 9.186.12.115 left intact
curl: (19) RETR response: 425
> QUIT
* FTP 0x29d5b2d0 state change from LIST to QUIT
< 221 Goodbye.
* FTP 0x29d5b2d0 state change from QUIT to STOP
* Closing connection #0
* SSLv3, TLS alert, Client hello (1):
--------
不知道是什么原因？
------解决方案--------------------------------------------------------
time out