Operations of communication between Docker containers and external network communication

Operations of communication between Docker containers and external network communication

Communication between containers

1. Network sharing of containers

Docker containers in this mode share a network stack so that two containers can communicate efficiently and quickly using localhost.

Used for communication between web servers and application servers. 

##Clear the experimental environment[root@server1 ~]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
 
##Create container with default network [root@server1 ~]# docker run -it --name vm1 ubuntu
root@b1a2a90f98a5:/# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
  link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
  inet 127.0.0.1/8 scope host lo
    valid_lft forever preferred_lft forever
368: eth0@if369: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
  link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff
  inet 172.17.0.2/16 brd 172.17.255.255 scope global eth0
    valid_lft forever preferred_lft forever
root@b1a2a90f98a5:/# [root@server1 ~]# 
 
##container creates vm2 that shares the network with vm1
[root@server1 ~]# docker run -it --name vm2 --network container:vm1 ubuntu
root@b1a2a90f98a5:/# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
  link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
  inet 127.0.0.1/8 scope host lo
    valid_lft forever preferred_lft forever
368: eth0@if369: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
  link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff
  inet 172.17.0.2/16 brd 172.17.255.255 scope global eth0
    valid_lft forever preferred_lft forever
root@b1a2a90f98a5:/#

2.--link method 

##Clear the image [root@server1 ~]# docker rm -f vm1
vm1
[root@server1 ~]# docker rm -f vm2
vm2
[root@server1 ~]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
 
##Default network creates vm1
[root@server1 ~]# docker run -it --name vm1 ubuntu
root@68e56c57a9a0:/# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
  link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
  inet 127.0.0.1/8 scope host lo
    valid_lft forever preferred_lft forever
370: eth0@if371: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
  link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff
  inet 172.17.0.2/16 brd 172.17.255.255 scope global eth0
    valid_lft forever preferred_lft forever
root@68e56c57a9a0:/# [root@server1 ~]#
 
##--link method to create container vm2 of vm1 subnet
[root@server1 ~]# docker run -it --name vm2 --link vm1:web ubuntu
root@61267851b484:/# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
  link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
  inet 127.0.0.1/8 scope host lo
    valid_lft forever preferred_lft forever
372: eth0@if373: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
  link/ether 02:42:ac:11:00:03 brd ff:ff:ff:ff:ff:ff
  inet 172.17.0.3/16 brd 172.17.255.255 scope global eth0 ##ip is in the same network segment as vm1, increasing valid_lft forever preferred_lft forever
 
##Parse the file containing vm1's ip and alias information root@61267851b484:/# cat /etc/hosts
127.0.0.1 localhost
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
172.17.0.2 web 68e56c57a9a0 vm1
172.17.0.3 61267851b484
root@61267851b484:/# ^C
root@61267851b484:/#

--link

Update the hosts file

The variables of the link container are also copied 

root@61267851b484:/#env
HOSTNAME=61267851b484
TERM=xterm
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arj=01;31:*.taz=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lz=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=00;36:*.au=00;36:*.flac=00;36:*.mid=00;36:*.midi=00;36:*.mka=00;36:*.mp3=00;36:*.mpc=00;36:*.ogg=00;36:*.ra=00;36:*.wav=00;36:*.axa=00;36:*.oga=00;36:*.spx=00;36:*.xspf=00;36:
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
PWD=/
SHLVL=1
HOME=/root
WEB_NAME=/vm2/web
LESSOPEN=| /usr/bin/lesspipe %s
LESSCLOSE=/usr/bin/lesspipe %s %s
_=/usr/bin/env
root@61267851b484:/#

When the container is stopped, the IP address will be released. When it is started again, other IP addresses will be acquired. The linked container will automatically update the hosts file.

Communication between the container and the external network

View the current iptable nat table firewall policy

[root@server1 ~]# iptables -t nat -nL
Chain PREROUTING (policy ACCEPT)
target prot opt ​​source destination     
DOCKER all -- 0.0.0.0/0 0.0.0.0/0 ADDRTYPE match dst-type LOCAL
 
Chain INPUT (policy ACCEPT)
target prot opt ​​source destination     
 
Chain OUTPUT (policy ACCEPT)
target prot opt ​​source destination     
DOCKER all -- 0.0.0.0/0 !127.0.0.0/8 ADDRTYPE match dst-type LOCAL
 
Chain POSTROUTING (policy ACCEPT)
target prot opt ​​source destination     
MASQUERADE all -- 172.26.0.0/24 0.0.0.0/0      
MASQUERADE all -- 172.20.0.0/16 0.0.0.0/0      
MASQUERADE all -- 172.18.0.0/16 0.0.0.0/0      
MASQUERADE all -- 172.17.0.0/16 0.0.0.0/0      
 
Chain DOCKER (2 references)
target prot opt ​​source destination     
RETURN all -- 0.0.0.0/0 0.0.0.0/0      
RETURN all -- 0.0.0.0/0 0.0.0.0/0      
RETURN all -- 0.0.0.0/0 0.0.0.0/0      
RETURN all -- 0.0.0.0/0 0.0.0.0/0
##Create nginx container and map port [root@server1 ~]# docker run -d --name nginx -p 80:80 nginx
cfefe6420cfe60c46cb7a050c142af7eff86fa6d687c3577077a5b4e2c8b961c
 
##Open port 80 [root@server1 ~]# docker port nginx 
80/tcp -> 0.0.0.0:80
 
[root@server1 ~]# netstat -antlp | grep 80
tcp6 0 0 :::80 :::* LISTEN 27094/docker-proxy 
[root@server1 ~]# iptables -t nat -nL
Chain PREROUTING (policy ACCEPT)
target prot opt ​​source destination     
DOCKER all -- 0.0.0.0/0 0.0.0.0/0 ADDRTYPE match dst-type LOCAL
 
Chain INPUT (policy ACCEPT)
target prot opt ​​source destination     
 
Chain OUTPUT (policy ACCEPT)
target prot opt ​​source destination     
DOCKER all -- 0.0.0.0/0 !127.0.0.0/8 ADDRTYPE match dst-type LOCAL
 
Chain POSTROUTING (policy ACCEPT)
target prot opt ​​source destination     
MASQUERADE all -- 172.26.0.0/24 0.0.0.0/0      
MASQUERADE all -- 172.20.0.0/16 0.0.0.0/0      
MASQUERADE all -- 172.18.0.0/16 0.0.0.0/0      
MASQUERADE all -- 172.17.0.0/16 0.0.0.0/0      
MASQUERADE tcp -- 172.17.0.2 172.17.0.2 tcp dpt:80
 
Chain DOCKER (2 references)
target prot opt ​​source destination     
RETURN all -- 0.0.0.0/0 0.0.0.0/0      
RETURN all -- 0.0.0.0/0 0.0.0.0/0      
RETURN all -- 0.0.0.0/0 0.0.0.0/0      
RETURN all -- 0.0.0.0/0 0.0.0.0/0      
DNAT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 to:172.17.0.2:80
[root@server1 ~]#

The above is my personal experience. I hope it can give you a reference. I also hope that you will support 123WORDPRESS.COM. If there are any mistakes or incomplete considerations, please feel free to correct me.

You may also be interested in:
  • Implementation of Docker container connection and communication
  • Detailed explanation of Docker container cross-host multi-network segment communication solution
  • Detailed explanation of direct routing in cross-host communication of Docker containers
  • Detailed explanation of how Docker containers communicate across hosts
  • Detailed explanation of a method of communication between docker containers
  • How to implement communication between Docker containers

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