Yes. I check the network in the server.
1、 I can ping the oursite web server.
PING any-fp.wa1.b.yahoo.com (67.195.160.76) 56(84) bytes of data.
64 bytes from ir1.fp.vip.ac4.yahoo.com (67.195.160.76): icmp_req=1 ttl=50 time=256 ms

2、 I write a python script to access the web then print the page, it works.

import urllib2
url="http://www.google.com.hk"
response = urllib2.urlopen('http://python.org/')
html = response.read()
print html

P.S. I have already stop the iptables service.

The sshd_config in the server contains the following:

#KerberosGetAFSToken no
#KerberosUseKuserok yes

UsePAM yes

# Accept locale-related environment variables
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
AcceptEnv XMODIFIERS

AllowAgentForwarding yes
AllowTcpForwarding yes
GatewayPorts clientspecified
#X11Forwarding no
X11Forwarding yes

#PidFile /var/run/sshd.pid
#MaxStartups 10
PermitTunnel yes
#ChrootDirectory none

# no default banner path
#Banner none

# override default of no subsystems
Subsystem sftp /usr/libexec/openssh/sftp-server

perhaps you have figured out your problem by now, but if not- I had this exact same issue
it turns out I had an SELinux policy blocking access

from a syslog message I got more info:
sealert -l 7d4d0ad5-b937-43df-a81d-8e04ec3c47e4

I used the suggested command
setsebool -P sshd_forward_ports 1

and everything works fine now

-Nate