两台linux服务器端口不通怎么解决

准备环境

启动一个web服务器，提供端口.

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[wyq@localhost ~]$ python -m SimpleHTTPServer 8080

Serving HTTP on 0.0.0.0 port 8080 ...

用其它web服务器提供端口也一样，由于python比较方便，这里就用它

1、使用telnet判断

telnet是windows标准服务，可以直接用；如果是linux机器，需要安装telnet.

用法: telnet ip port

1）先用telnet连接不存在的端口

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[root@localhost ~]# telnet 10.0.250.3 80

Trying 10.0.250.3...

telnet: connect to address 10.0.250.3: Connection refused #直接提示连接被拒绝

2）再连接存在的端口

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[root@localhost ~]# telnet localhost 22

Trying ::1...

Connected to localhost. #看到Connected就连接成功了

Escape character is '^]'.

SSH-2.0-OpenSSH_5.3

a

Protocol mismatch.

Connection closed by foreign host.

2、使用ssh判断

ssh是linux的标准配置并且最常用，可以用来判断端口吗？

用法: ssh -v -p port username@ip

-v 调试模式(会打印日志).

-p 指定端口

username可以随意

1）连接不存在端口

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[root@localhost ~]# ssh 10.0.250.3 -p 80

ssh: connect to host 10.0.250.3 port 80: Connection refused

[root@localhost ~]# ssh 10.0.250.3 -p 80 -v

OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013

debug1: Reading configuration data /etc/ssh/ssh_config

debug1: Applying options for *

debug1: Connecting to 10.0.250.3 [10.0.250.3] port 80.

debug1: connect to address 10.0.250.3 port 80: Connection refused

ssh: connect to host 10.0.250.3 port 80: Connection refused

2）连接存在的端口

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[root@localhost ~]# ssh ... -p

a

^]

^C

[root@localhost ~]# ssh ... -p -v

OpenSSH_.p, OpenSSL ..e-fips Feb

debug: Reading configuration data /etc/ssh/ssh_config

debug: Applying options for *

debug: Connecting to ... [...] port .

debug: Connection established.

debug: permanently_set_uid: /

debug: identity file /root/.ssh/identity type -

debug: identity file /root/.ssh/identity-cert type -

debug: identity file /root/.ssh/id_rsa type -

debug: identity file /root/.ssh/id_rsa-cert type -

debug: identity file /root/.ssh/id_dsa type -

debug: identity file /root/.ssh/id_dsa-cert type -

a

^C

不用-v选项也可以咯

3、使用wget判断

wget是linux下的下载工具，需要先安装.

用法: wget ip:port

1）连接不存在的端口

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[root@localhost ~]# wget ...:

---- ::-- http://.../

Connecting to ...:... failed: Connection refused.

2）连接存在的端口

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[root@localhost ~]# wget ...:

---- ::-- http://...:/

Connecting to ...:... connected.

HTTP request sent, awaiting response...

4、使用端口扫描工具

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[root@localhost ~]# nmap ... -p

Starting Nmap . ( http://nmap.org ) at -- : CST

Nmap scan report for ...

Host is up (.s latency).

PORT STATE SERVICE

/tcp closed http

MAC Address: B:A::CF:FD:D (Unknown)

Nmap done: IP address ( host up) scanned in . seconds

[root@localhost ~]# nmap ... -p

Starting Nmap . ( http://nmap.org ) at -- : CST

Nmap scan report for ...

Host is up (.s latency).

PORT STATE SERVICE

/tcp open http-proxy

MAC Address: B:A::CF:FD:D (Unknown)

Nmap done: IP address ( host up) scanned in . seconds

[root@localhost ~]# nmap ...

Starting Nmap . ( http://nmap.org ) at -- : CST

Nmap scan report for ...

Host is up (.s latency).

Not shown: closed ports

PORT STATE SERVICE

/tcp open ssh

/tcp open rpcbind

/tcp open http-proxy

/tcp open unknown

MAC Address: B:A::CF:FD:D (Unknown)

Nmap done: IP address ( host up) scanned in . seconds

总结

提供端口服务，则使用了tcp协议，上面是以web服务器为例。如果服务器是更简单的tcp服务器，三个工具同样适用.

三个工具的共同点是：1.以tcp协议为基础；2.能访问指定端口. 遵循这两点可以找到很多工具.

一般在windows下使用telnet比较方便，linux下个人就比较喜欢用wget.

1，关闭IPtables防火墙，关闭selinux

2，查看防火墙等网安设备的规则及日志，看是否有拦截或过滤。

3，查检服务器的系统变量，有可能是由这些变量导致的，尝试把这些变量删除或注释。

如下变量：

默认情况下 sysctl.conf 文件里面是没有配置变量的。

vim /etc/sysctl.conf

net.core.rmem_max=16777216

net.core.wmem_max=16777216

net.core.netdev_max_backlog = 32768

net.core.somaxconn = 262144

net.ipv4.tcp_fin_timeout = 30

net.ipv4.tcp_keepalive_time = 30

net.ipv4.tcp_keepalive_intvl = 30

net.ipv4.tcp_keepalive_probes = 3

net.ipv4.tcp_rmem=4096 87380 16777216

net.ipv4.tcp_wmem=4096 65536 16777216

net.ipv4.tcp_syncookies = 1

net.ipv4.tcp_tw_reuse = 1

net.ipv4.tcp_tw_recycle = 1

net.ipv4.tcp_max_syn_backlog = 262144

net.ipv4.tcp_max_tw_buckets = 5000

net.ipv4.ip_local_port_range = 1024 65000

net.ipv4.tcp_synack_retries = 2

net.ipv4.tcp_syn_retries = 2

net.netfilter.nf_conntrack_max = 655360

kernel.ctrl-alt-del = 1

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