我在编写上一个Shell脚本时，有网友问我：怎么把脚本1723端口改成其它的，在本地win还能正常连接？1723端口容易被封
计算机网络技术中，端口（Port）指逻辑意义上用于区分服务的端口，如TCP/IP协议中的服务端口，端口号的范围从0到65535，比如用于浏览网页服务的80端口，用于FTP服务的21端口等，用于PPTP VPN连接的端口号是1723。为了对端口进行区分，将每个端口进行了编号。
我在这里用一个例子说明，例如有一台服务器计算机名：Fserver，IP地址是：192.168.1.200，这台服务器功能有文件服务器、Mysql数据库、Web服务器、PPTP VPN服务……，那么我们访问这台服务器的不同功能将是通过端口（Port）来区分的。
例如：
192.168.1.200:21 FTP服务端口（默认）；
192.168.1.200:80 WEB服务端口（默认）；
192.168.1.200:3306 Mysql数据库服务端口（默认）；
192.168.1.200:1723 PPTP VPN服务端口（默认）；
用通俗易懂的解释：你可以把IP理解成一幢大楼，而每个房间号可理解为端口（Port），从0到65535，每个房间住不同的居民，提供各种不同的服务……。
【端口默认定义说明】
针对该网友的提问，我查了查资料，在CentOS7操作系统中，有一文件定义了0~65536端口的默认定义，希望能对大家有所帮助！
操作方式：
vim /etc/services
vim /etc/services查看或修改端口截图
【/etc/services文件部分内容】由于文章长度有限，只能放出部分……
ill 1611/tcp # Inter Library Loan
ill 1611/udp # Inter Library Loan
netbill-trans 1612/tcp # NetBill Transaction Server
netbill-trans 1612/udp # NetBill Transaction Server
netbill-keyrep 1613/tcp # NetBill Key Repository
netbill-keyrep 1613/udp # NetBill Key Repository
netbill-cred 1614/tcp # NetBill Credential Server
netbill-cred 1614/udp # NetBill Credential Server
netbill-auth 1615/tcp # NetBill Authorization Server
netbill-auth 1615/udp # NetBill Authorization Server
netbill-prod 1616/tcp # NetBill Product Server
netbill-prod 1616/udp # NetBill Product Server
nimrod-agent 1617/tcp # Nimrod Inter-Agent Communication
nimrod-agent 1617/udp # Nimrod Inter-Agent Communication
skytelnet 1618/tcp # skytelnet
skytelnet 1618/udp # skytelnet
xs-openstorage 1619/tcp # xs-openstorage
xs-openstorage 1619/udp # xs-openstorage
faxportwinport 1620/tcp # faxportwinport
faxportwinport 1620/udp # faxportwinport
softdataphone 1621/tcp # softdataphone
softdataphone 1621/udp # softdataphone
ontime 1622/tcp # ontime
ontime 1622/udp # ontime
jaleosnd 1623/tcp # jaleosnd
jaleosnd 1623/udp # jaleosnd
udp-sr-port 1624/tcp # udp-sr-port
udp-sr-port 1624/udp # udp-sr-port
svs-omagent 1625/tcp # svs-omagent
svs-omagent 1625/udp # svs-omagent
shockwave 1626/tcp # Shockwave
shockwave 1626/udp # Shockwave
t128-gateway 1627/tcp # T.128 Gateway
t128-gateway 1627/udp # T.128 Gateway
lontalk-norm 1628/tcp # LonTalk normal
lontalk-norm 1628/udp # LonTalk normal
lontalk-urgnt 1629/tcp # LonTalk urgent
lontalk-urgnt 1629/udp # LonTalk urgent
oraclenet8cman 1630/tcp # Oracle Net8 Cman
oraclenet8cman 1630/udp # Oracle Net8 Cman
visitview 1631/tcp # Visit view
visitview 1631/udp # Visit view
pammratc 1632/tcp # PAMMRATC
pammratc 1632/udp # PAMMRATC
pammrpc 1633/tcp # PAMMRPC
pammrpc 1633/udp # PAMMRPC
loaprobe 1634/tcp # Log On America Probe
loaprobe 1634/udp # Log On America Probe
edb-server1 1635/tcp # EDB Server 1
edb-server1 1635/udp # EDB Server 1
isdc 1636/tcp # ISP shared public data control
isdc 1636/udp # ISP shared public data control
islc 1637/tcp # ISP shared local data control
islc 1637/udp # ISP shared local data control
ismc 1638/tcp # ISP shared management control
ismc 1638/udp # ISP shared management control
cert-initiator 1639/tcp # cert-initiator
cert-initiator 1639/udp # cert-initiator
cert-responder 1640/tcp # cert-responder
cert-responder 1640/udp # cert-responder
invision 1641/tcp # InVision
invision 1641/udp # InVision
isis-am 1642/tcp # isis-am
isis-am 1642/udp # isis-am
isis-ambc 1643/tcp # isis-ambc
isis-ambc 1643/udp # isis-ambc
saiseh 1644/tcp # Satellite-data Acquisition System 4
saiseh 1644/udp # Satellite-data Acquisition System 4
rsap 1647/tcp # rsap
rsap 1647/udp # rsap
concurrent-lm 1648/tcp # concurrent-lm
concurrent-lm 1648/udp # concurrent-lm
nkd 1650/tcp # nkdn
nkd 1650/udp # nkd
shiva_confsrvr 1651/tcp shiva-confsrvr # shiva_confsrvr
shiva_confsrvr 1651/udp shiva-confsrvr # shiva_confsrvr
xnmp 1652/tcp # xnmp
xnmp 1652/udp # xnmp
alphatech-lm 1653/tcp # alphatech-lm
alphatech-lm 1653/udp # alphatech-lm
stargatealerts 1654/tcp # stargatealerts
stargatealerts 1654/udp # stargatealerts
dec-mbadmin 1655/tcp # dec-mbadmin
dec-mbadmin 1655/udp # dec-mbadmin
dec-mbadmin-h 1656/tcp # dec-mbadmin-h
dec-mbadmin-h 1656/udp # dec-mbadmin-h
fujitsu-mmpdc 1657/tcp # fujitsu-mmpdc
fujitsu-mmpdc 1657/udp # fujitsu-mmpdc
sixnetudr 1658/tcp # sixnetudr
sixnetudr 1658/udp # sixnetudr
sg-lm 1659/tcp # Silicon Grail License Manager
sg-lm 1659/udp # Silicon Grail License Manager
skip-mc-gikreq 1660/tcp # skip-mc-gikreq
skip-mc-gikreq 1660/udp # skip-mc-gikreq
netview-aix-1 1661/tcp # netview-aix-1
netview-aix-1 1661/udp # netview-aix-1
netview-aix-2 1662/tcp # netview-aix-2
netview-aix-2 1662/udp # netview-aix-2
netview-aix-3 1663/tcp # netview-aix-3
netview-aix-3 1663/udp # netview-aix-3
netview-aix-4 1664/tcp # netview-aix-4
netview-aix-4 1664/udp # netview-aix-4
netview-aix-5 1665/tcp # netview-aix-5
netview-aix-5 1665/udp # netview-aix-5
netview-aix-6 1666/tcp # netview-aix-6
netview-aix-6 1666/udp # netview-aix-6
netview-aix-7 1667/tcp # netview-aix-7
netview-aix-7 1667/udp # netview-aix-7
netview-aix-8 1668/tcp # netview-aix-8
netview-aix-8 1668/udp # netview-aix-8
netview-aix-9 1669/tcp # netview-aix-9
netview-aix-9 1669/udp # netview-aix-9
netview-aix-10 1670/tcp # netview-aix-10
netview-aix-10 1670/udp # netview-aix-10
netview-aix-11 1671/tcp # netview-aix-11
netview-aix-11 1671/udp # netview-aix-11
netview-aix-12 1672/tcp # netview-aix-12
netview-aix-12 1672/udp # netview-aix-12
proshare-mc-1 1673/tcp # Intel Proshare Multicast
proshare-mc-1 1673/udp # Intel Proshare Multicast
proshare-mc-2 1674/tcp # Intel Proshare Multicast
proshare-mc-2 1674/udp # Intel Proshare Multicast
pdp 1675/tcp # Pacific Data Products
pdp 1675/udp # Pacific Data Products
netcomm1 1676/tcp # netcomm1
netcomm2 1676/udp # netcomm2
groupwise 1677/tcp # groupwise
groupwise 1677/udp # groupwise
prolink 1678/tcp # prolink
prolink 1678/udp # prolink
darcorp-lm 1679/tcp # darcorp-lm
darcorp-lm 1679/udp # darcorp-lm
microcom-sbp 1680/tcp # microcom-sbp
microcom-sbp 1680/udp # microcom-sbp
sd-elmd 1681/tcp # sd-elmd
sd-elmd 1681/udp # sd-elmd
lanyon-lantern 1682/tcp # lanyon-lantern
lanyon-lantern 1682/udp # lanyon-lantern
ncpm-hip 1683/tcp # ncpm-hip
ncpm-hip 1683/udp # ncpm-hip
snaresecure 1684/tcp # SnareSecure
snaresecure 1684/udp # SnareSecure
n2nremote 1685/tcp # n2nremote
n2nremote 1685/udp # n2nremote
cvmon 1686/tcp # cvmon
cvmon 1686/udp # cvmon
nsjtp-ctrl 1687/tcp # nsjtp-ctrl
nsjtp-ctrl 1687/udp # nsjtp-ctrl
nsjtp-data 1688/tcp # nsjtp-data
nsjtp-data 1688/udp # nsjtp-data
firefox 1689/tcp # firefox
firefox 1689/udp # firefox
ng-umds 1690/tcp # ng-umds
ng-umds 1690/udp # ng-umds
empire-empuma 1691/tcp # empire-empuma
empire-empuma 1691/udp # empire-empuma
sstsys-lm 1692/tcp # sstsys-lm
sstsys-lm 1692/udp # sstsys-lm
rrirtr 1693/tcp # rrirtr
rrirtr 1693/udp # rrirtr
rrimwm 1694/tcp # rrimwm
rrimwm 1694/udp # rrimwm
rrilwm 1695/tcp # rrilwm
rrilwm 1695/udp # rrilwm
rrifmm 1696/tcp # rrifmm
rrifmm 1696/udp # rrifmm
rrisat 1697/tcp # rrisat
rrisat 1697/udp # rrisat
rsvp-encap-1 1698/tcp # RSVP-ENCAPSULATION-1
rsvp-encap-1 1698/udp # RSVP-ENCAPSULATION-1
rsvp-encap-2 1699/tcp # RSVP-ENCAPSULATION-2
rsvp-encap-2 1699/udp # RSVP-ENCAPSULATION-2
mps-raft 1700/tcp # mps-raft
mps-raft 1700/udp # mps-raft
deskshare 1702/tcp # deskshare
deskshare 1702/udp # deskshare
hb-engine 1703/tcp # hb-engine
hb-engine 1703/udp # hb-engine
bcs-broker 1704/tcp # bcs-broker
bcs-broker 1704/udp # bcs-broker
slingshot 1705/tcp # slingshot
slingshot 1705/udp # slingshot
jetform 1706/tcp # jetform
jetform 1706/udp # jetform
vdmplay 1707/tcp # vdmplay
vdmplay 1707/udp # vdmplay
gat-lmd 1708/tcp # gat-lmd
gat-lmd 1708/udp # gat-lmd
centra 1709/tcp # centra
centra 1709/udp # centra
impera 1710/tcp # impera
impera 1710/udp # impera
pptconference 1711/tcp # pptconference
pptconference 1711/udp # pptconference
registrar 1712/tcp # resource monitoring service
registrar 1712/udp # resource monitoring service
conferencetalk 1713/tcp # ConferenceTalk
conferencetalk 1713/udp # ConferenceTalk
sesi-lm 1714/tcp # sesi-lm
sesi-lm 1714/udp # sesi-lm
houdini-lm 1715/tcp # houdini-lm
houdini-lm 1715/udp # houdini-lm
xmsg 1716/tcp # xmsg
xmsg 1716/udp # xmsg
fj-hdnet 1717/tcp # fj-hdnet
fj-hdnet 1717/udp # fj-hdnet
caicci 1721/tcp # caicci
caicci 1721/udp # caicci
hks-lm 1722/tcp # HKS License Manager
hks-lm 1722/udp # HKS License Manager
pptp 1723/tcp # pptp
pptp 1723/udp # pptp
csbphonemaster 1724/tcp # csbphonemaster
csbphonemaster 1724/udp # csbphonemaster
iden-ralp 1725/tcp # iden-ralp
iden-ralp 1725/udp # iden-ralp
iberiagames 1726/tcp # IBERIAGAMES
iberiagames 1726/udp # IBERIAGAMES
winddx 1727/tcp # winddx
winddx 1727/udp # winddx
telindus 1728/tcp # TELINDUS
telindus 1728/udp # TELINDUS
citynl 1729/tcp # CityNL License Management
citynl 1729/udp # CityNL License Management
roketz 1730/tcp # roketz
roketz 1730/udp # roketz
msiccp 1731/tcp # MSICCP
msiccp 1731/udp # MSICCP
proxim 1732/tcp # proxim
proxim 1732/udp # proxim
siipat 1733/tcp # SIMS - SIIPAT Protocol for Alarm Transmission
siipat 1733/udp # SIMS - SIIPAT Protocol for Alarm Transmission
cambertx-lm 1734/tcp # Camber Corporation License Management
cambertx-lm 1734/udp # Camber Corporation License Management
privatechat 1735/tcp # PrivateChat
privatechat 1735/udp # PrivateChat
street-stream 1736/tcp # street-stream
street-stream 1736/udp # street-stream
ultimad 1737/tcp # ultimad
ultimad 1737/udp # ultimad
gamegen1 1738/tcp # GameGen1
gamegen1 1738/udp # GameGen1
webaccess 1739/tcp # webaccess
webaccess 1739/udp # webaccess
encore 1740/tcp # encore
encore 1740/udp # encore
cisco-net-mgmt 1741/tcp # cisco-net-mgmt
cisco-net-mgmt 1741/udp # cisco-net-mgmt
3Com-nsd 1742/tcp # 3Com-nsd
3Com-nsd 1742/udp # 3Com-nsd
cinegrfx-lm 1743/tcp # Cinema Graphics License Manager
cinegrfx-lm 1743/udp # Cinema Graphics License Manager
ncpm-ft 1744/tcp # ncpm-ft
ncpm-ft 1744/udp # ncpm-ft
remote-winsock 1745/tcp # remote-winsock
remote-winsock 1745/udp # remote-winsock
ftrapid-1 1746/tcp # ftrapid-1
ftrapid-1 1746/udp # ftrapid-1
ftrapid-2 1747/tcp # ftrapid-2
ftrapid-2 1747/udp # ftrapid-2
oracle-em1 1748/tcp # oracle-em1
oracle-em1 1748/udp # oracle-em1
aspen-services 1749/tcp # aspen-services
aspen-services 1749/udp # aspen-services
sslp 1750/tcp # Simple Socket Library's PortMaster
sslp 1750/udp # Simple Socket Library's PortMaster
swiftnet 1751/tcp # SwiftNet
swiftnet 1751/udp # SwiftNet
lofr-lm 1752/tcp # Leap of Faith Research License Manager
lofr-lm 1752/udp # Leap of Faith Research License Manager
predatar-comms 1753/tcp # Predatar Comms Service
oracle-em2 1754/tcp # oracle-em2
oracle-em2 1754/udp # oracle-em2
ms-streaming 1755/tcp # ms-streaming
ms-streaming 1755/udp # ms-streaming
capfast-lmd 1756/tcp # capfast-lmd
capfast-lmd 1756/udp # capfast-lmd
cnhrp 1757/tcp # cnhrp
cnhrp 1757/udp # cnhrp
spss-lm 1759/tcp # SPSS License Manager
www-ldap-gw 1760/tcp # www-ldap-gw
www-ldap-gw 1760/udp # www-ldap-gw
cft-0 1761/tcp # cft-0
cft-0 1761/udp # cft-0
cft-1 1762/tcp # cft-1
cft-1 1762/udp # cft-1
cft-2 1763/tcp # cft-2
cft-2 1763/udp # cft-2
cft-3 1764/tcp # cft-3
cft-3 1764/udp # cft-3
cft-4 1765/tcp # cft-4
cft-4 1765/udp # cft-4
cft-5 1766/tcp # cft-5
cft-5 1766/udp # cft-5
cft-6 1767/tcp # cft-6
cft-6 1767/udp # cft-6
cft-7 1768/tcp # cft-7
cft-7 1768/udp # cft-7
bmc-net-adm 1769/tcp # bmc-net-adm
bmc-net-adm 1769/udp # bmc-net-adm
bmc-net-svc 1770/tcp # bmc-net-svc
bmc-net-svc 1770/udp # bmc-net-svc
vaultbase 1771/tcp # vaultbase
