我买了一个VPS并在上面搭建了一个shadowsocks服务器。它运行了大约两个月，突然无法工作，即我无法使用它克服 GFW。所以我检查了服务器，重新安装了所有东西，检查了防火墙，但仍然无法解决问题。请帮我解决这个难题！
首先，我可以通过 ssh 连接到服务器。我使用的是mac，服务器操作系统是CentOS7。
我尝试从 mac ping 服务器，它已连接。
PING vultr (108.61.215.163): 56 data bytes
64 bytes from 108.61.215.163: icmp_seq=0 ttl=50 time=485.473 ms
64 bytes from 108.61.215.163: icmp_seq=1 ttl=50 time=407.054 ms
64 bytes from 108.61.215.163: icmp_seq=2 ttl=50 time=429.089 ms
64 bytes from 108.61.215.163: icmp_seq=3 ttl=50 time=552.046 ms
^C
--- vultr ping statistics ---
5 packets transmitted, 4 packets received, 20.0% packet loss
round-trip min/avg/max/stddev = 407.054/468.416/552.046/56.118 ms
然后我用我在shadowsocks中定义的特定端口telnet它，但连接失败。
# telnet 108.61.216.163 8754
Trying 108.61.215.163...
telnet: connect to address 108.61.215.163: Operation timed out
telnet: Unable to connect to remote host
所以我从服务器检查 netstat：
# netstat -anltp
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 3253/sshd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 3498/master
tcp 0 0 108.61.215.163:8754 0.0.0.0:* LISTEN 3652/python
tcp 0 0 108.61.215.163:22 218.92.1.158:45819 SYN_RECV -
tcp 0 21 108.61.215.163:22 150.162.11.207:43510 ESTABLISHED 3847/sshd: [accepte
tcp 0 0 108.61.215.163:22 58.49.194.24:55529 ESTABLISHED 3793/sshd: root@pts
tcp 0 1281 108.61.215.163:22 218.92.1.158:19746 FIN_WAIT1 -
tcp 0 1280 108.61.215.163:22 36.156.24.99:50400 ESTABLISHED 3843/sshd: [accepte
tcp 0 0 108.61.215.163:8754 58.49.194.24:56578 SYN_RECV -
tcp6 0 0 :::22 :::* LISTEN 3253/sshd
tcp6 0 0 ::1:25 :::* LISTEN 3498/master
端口是8754，PID3652是我的shadowsocks服务。
我还检查了我的防火墙设置，端口 8754 已打开，
# firewall-cmd --list-all
public (active)
target: default
icmp-block-inversion: no
interfaces: eth0
sources:
services: dhcpv6-client ssh http https
ports: 8754/tcp
protocols:
masquerade: no
forward-ports:
source-ports:
icmp-blocks:
rich rules:
rule family="ipv4" port port="8754" protocol="tcp" accept
我还检查了 iptables，这是返回的内容：
# iptables -xvn -L
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
349 31354 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0
63 2928 INPUT_direct all -- * * 0.0.0.0/0 0.0.0.0/0
63 2928 INPUT_ZONES_SOURCE all -- * * 0.0.0.0/0 0.0.0.0/0
63 2928 INPUT_ZONES all -- * * 0.0.0.0/0 0.0.0.0/0
1 44 DROP all -- * * 0.0.0.0/0 0.0.0.0/0 ctstate INVALID
47 1972 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0
0 0 FORWARD_direct all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 FORWARD_IN_ZONES_SOURCE all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 FORWARD_IN_ZONES all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 FORWARD_OUT_ZONES_SOURCE all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 FORWARD_OUT_ZONES all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 DROP all -- * * 0.0.0.0/0 0.0.0.0/0 ctstate INVALID
0 0 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
Chain OUTPUT (policy ACCEPT 408 packets, 71561 bytes)
pkts bytes target prot opt in out source destination
410 71641 OUTPUT_direct all -- * * 0.0.0.0/0 0.0.0.0/0
Chain FORWARD_IN_ZONES (1 references)
pkts bytes target prot opt in out source destination
0 0 FWDI_public all -- eth0 * 0.0.0.0/0 0.0.0.0/0 [goto]
0 0 FWDI_public all -- + * 0.0.0.0/0 0.0.0.0/0 [goto]
Chain FORWARD_IN_ZONES_SOURCE (1 references)
pkts bytes target prot opt in out source destination
Chain FORWARD_OUT_ZONES (1 references)
pkts bytes target prot opt in out source destination
0 0 FWDO_public all -- * eth0 0.0.0.0/0 0.0.0.0/0 [goto]
0 0 FWDO_public all -- * + 0.0.0.0/0 0.0.0.0/0 [goto]
Chain FORWARD_OUT_ZONES_SOURCE (1 references)
pkts bytes target prot opt in out source destination
Chain FORWARD_direct (1 references)
pkts bytes target prot opt in out source destination
Chain FWDI_public (2 references)
pkts bytes target prot opt in out source destination
0 0 FWDI_public_log all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 FWDI_public_deny all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 FWDI_public_allow all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0
Chain FWDI_public_allow (1 references)
pkts bytes target prot opt in out source destination
Chain FWDI_public_deny (1 references)
pkts bytes target prot opt in out source destination
Chain FWDI_public_log (1 references)
pkts bytes target prot opt in out source destination
Chain FWDO_public (2 references)
pkts bytes target prot opt in out source destination
0 0 FWDO_public_log all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 FWDO_public_deny all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 FWDO_public_allow all -- * * 0.0.0.0/0 0.0.0.0/0
Chain FWDO_public_allow (1 references)
pkts bytes target prot opt in out source destination
Chain FWDO_public_deny (1 references)
pkts bytes target prot opt in out source destination
Chain FWDO_public_log (1 references)
pkts bytes target prot opt in out source destination
Chain INPUT_ZONES (1 references)
pkts bytes target prot opt in out source destination
61 2800 IN_public all -- eth0 * 0.0.0.0/0 0.0.0.0/0 [goto]
2 128 IN_public all -- + * 0.0.0.0/0 0.0.0.0/0 [goto]
Chain INPUT_ZONES_SOURCE (1 references)
pkts bytes target prot opt in out source destination
Chain INPUT_direct (1 references)
pkts bytes target prot opt in out source destination
Chain IN_public (2 references)
pkts bytes target prot opt in out source destination
63 2928 IN_public_log all -- * * 0.0.0.0/0 0.0.0.0/0
63 2928 IN_public_deny all -- * * 0.0.0.0/0 0.0.0.0/0
63 2928 IN_public_allow all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0
Chain IN_public_allow (1 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:8754 ctstate NEW
15 912 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:22 ctstate NEW
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 ctstate NEW
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:443 ctstate NEW
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:8754 ctstate NEW
Chain IN_public_deny (1 references)
pkts bytes target prot opt in out source destination
Chain IN_public_log (1 references)
pkts bytes target prot opt in out source destination
Chain OUTPUT_direct (1 references)
pkts bytes target prot opt in out source destination
我现在不知道要检查什么或做什么...请指教...非常感谢！
看起来像是收到了
SYNtcp 0 0 108.61.215.163:8754 58.49.194.24:56578 SYN_RECV -
我认为这意味着防火墙允许新连接（SYN）。另一种验证方法是暂时禁用防火墙并尝试连接/代理。如果还是不行，那么你应该检查
shadowsocks