在客户端配置TNS测试报错ORA-12170:TNS:连接超时

在Red Hat Enterprise Linux Server Releae 5.5 成功安装ORACLE 10g 后，在客户端配置TNS后，测试是否可以连接到数据块服务器，结果报错： ORA-12170：TNS：连接超时

1：首先检查网络是否能ping通，如下所示，网络是畅通的 

2：检查TNS配置（TNS配置也没有问题） 
GSP = 
(DESCRIPTION = 
(ADDRESS =(PROTOCOL = TCP)(HOST = 172.20.36.79)(PORT = 1521)) 
(CONNECT_DATA= 
(SERVER = DEDICATED) 
(SERVICE_NAME = gsp) 
) 
) 

3：查看服务器监听服务是否启动 
[oracle@wgods ~]$ lsnrctl status 
LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 14-DEC-2012 15:51:13 
Copyright (c) 1991, 2005, Oracle. All rights reserved. 
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1))) 
STATUS of the LISTENER 
------------------------ 
Alias LISTENER 
Version TNSLSNR for Linux: Version 10.2.0.1.0 - Production 
Start Date 14-DEC-2012 13:15:28 
Uptime 0 days 2 hr. 35 min. 45 sec 
Trace Level off 
Security ON: Local OS Authentication 
SNMP OFF 
Listener Parameter File /database/oracle/product/dbhome/network/admin/listener.ora 
Listener Log File /database/oracle/product/dbhome/network/log/listener.log 
Listening Endpoints Summary... 
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1))) 
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=wgods)(PORT=1521))) 
Services Summary... 
Service "PLSExtProc" has 1 instance(s). 
Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service... 
Service "gsp" has 2 instance(s). 
Instance "gsp", status UNKNOWN, has 1 handler(s) for this service... 
Instance "gsp", status READY, has 1 handler(s) for this service... 
Service "gspXDB" has 1 instance(s). 
Instance "gsp", status READY, has 1 handler(s) for this service... 
Service "gsp_XPT" has 1 instance(s). 
Instance "gsp", status READY, has 1 handler(s) for this service... 
The command completed successfully 

4：使用tnsping命令检查，报TNS-12535: TNS: 操作超时，这时我们可以肯定是防火墙的问题了 
C:\Users\kerry>tnsping 172.20.32.79 
TNS Ping Utility for 32-bit Windows: Version 11.2.0.1.0 - Production on 14-12月-2012 15:47:15 
Copyright (c) 1997, 2010, Oracle. All rights reserved. 
已使用的参数文件: 
E:\app\kerry\product\11.2.0\dbhome_1\network\admin\sqlnet.ora 
已使用 EZCONNECT 适配器来解析别名 
尝试连接 (DESCRIPTION=(CONNECT_DATA=(SERVICE_NAME=))(ADDRESS=(PROTOCOL=TCP)(HOST=172.20.32.79)(PORT=1521))) 
TNS-12535: TNS: 操作超时 
对于防火墙问题，我们可以有两种解决方案： 
1：关闭防火墙（这种方案不怎么好，关闭防火墙，会带来许多安全隐患） 
[root@wgods ~]# service iptables stop 
Flushing firewall rules: [ OK ] 
Setting chains to policy ACCEPT: filter [ OK ] 
Unloading iptables modules: [ OK ] 

2：修改iptables，开放1521端口，允许1521端口被连接 
2.1 编辑iptables文件，添加-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 1521 -j ACCEPT记录。 
[root@wgods sysconfig]# vi iptables 
# Generated by iptables-save v1.3.5 on Fri Dec 14 17:03:58 2012 
*filter 
:INPUT ACCEPT [0:0] 
:FORWARD ACCEPT [0:0] 
:OUTPUT ACCEPT [1749:243629] 
:RH-Firewall-1-INPUT - [0:0] 
-A INPUT -j RH-Firewall-1-INPUT 
-A FORWARD -j RH-Firewall-1-INPUT 
-A RH-Firewall-1-INPUT -i lo -j ACCEPT 
-A RH-Firewall-1-INPUT -p icmp -m icmp --icmp-type any -j ACCEPT 
-A RH-Firewall-1-INPUT -p esp -j ACCEPT 
-A RH-Firewall-1-INPUT -p ah -j ACCEPT 
-A RH-Firewall-1-INPUT -d 224.0.0.251 -p udp -m udp --dport 5353 -j ACCEPT 
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT 
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT 
-A RH-Firewall-1-INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT 
-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 21 -j ACCEPT 
-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 25 -j ACCEPT 
-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT 
-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 23 -j ACCEPT 
-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 1521 -j ACCEPT 
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited 
COMMIT 
# Completed on Fri Dec 14 17:03:58 2012 
~ 
~ 
~ 
~ 
~ 
"iptables" 24L, 1212C written 

2.2 重启iptables服务 
[root@wgods sysconfig]# service iptables restart 
Flushing firewall rules: [ OK ] 
Setting chains to policy ACCEPT: filter [ OK ] 
Unloading iptables modules: [ OK ] 
Applying iptables firewall rules: [ OK ] 
Loading additional iptables modules: ip_conntrack_netbios_ns ip_conntrack_ftp [ OK ] 
2.3 保存新增的规则，以免下次重启机器后，配置规则失效 
[root@wgods sysconfig]# service iptables save 
Saving firewall rules to /etc/sysconfig/iptables: [ OK ] 
2.4 查看1521端口是否开放，允许连接（见红色部分） 
[root@wgods sysconfig]# iptables -L -n 
Chain INPUT (policy ACCEPT) 
target prot opt source destination 
RH-Firewall-1-INPUT all -- 0.0.0.0/0 0.0.0.0/0 
Chain FORWARD (policy ACCEPT) 
target prot opt source destination 
RH-Firewall-1-INPUT all -- 0.0.0.0/0 0.0.0.0/0 
Chain OUTPUT (policy ACCEPT) 
target prot opt source destination 
Chain RH-Firewall-1-INPUT (2 references) 
target prot opt source destination 
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 
ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0 icmp type 255 
ACCEPT esp -- 0.0.0.0/0 0.0.0.0/0 
ACCEPT ah -- 0.0.0.0/0 0.0.0.0/0 
ACCEPT udp -- 0.0.0.0/0 224.0.0.251 udp dpt:5353 
ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:631 
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:631 
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:21 
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:25 
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:22 
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:23 
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:1521 
REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited 
[root@wgods sysconfig]# 
从客户端用PL/SQL Developer连接数据库，问题解决。