This is the error log

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Thu May 2 01:05:14 2013 218.86.195.206:28387 TLS: Initial packet from [AF_INET]218.86.195.206:28387, sid=86eac8aa 05140769
Thu May 2 01:06:14 2013 218.86.195.206:28280 TLS: Initial packet from [AF_INET]218.86.195.206:28280, sid=aa44605d 2b4edba3
Thu May 2 01:06:14 2013 218.86.195.206:28387 TLS Error: TLS key negotiation failed to occur within 60 seconds (check your network connectivity)
Thu May 2 01:06:14 2013 218.86.195.206:28387 TLS Error: TLS handshake failed
Thu May 2 01:06:14 2013 218.86.195.206:28387 SIGUSR1[soft,tls-error] received, client-instance restarting

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and this is my openvpn config

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port 11994
proto udp
dev tun

# SSL/TLS
ca /etc/openvpn/ca.crt
cert /etc/openvpn/zfish.crt
key /etc/openvpn/zfish.key

tls-auth /etc/openvpn/ta.key 0

# Diffie hellman parameters
dh /etc/openvpn/dh2048.pem
script-security 2
keepalive 10 120
comp-lzo
# VPN subnet
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist /etc/openvpn/ipp.txt
persist-key
persist-tun
status /var/log/openvpn-status.log
verb 3
push "redirect-gateway def1"
push "dhcp-option DNS 10.8.0.1"
push "dhcp-option DNS 8.8.8.8"
push "dhcp-option DNS 4.4.4.4"
#push "dhcp-option DNS 208.67.222.222"

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and this is my andriod client config

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#!/bin/sh
client

dev tun
proto udp
remote 106.187.49.162 11994
nobind
persist-key
persist-tun
ca ca.crt
cert MX2.crt
key MX2.key

tls-auth ta.key 1
auth-user-pass

verb 3

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Please help me, Thanks very much!