At least in the UNIX context, there is a real difference between
ports and sockets, although they are very similar. I tend to think
that Apple and Novell have confused the usage, although without
looking into their OS implementation, there may be a reason for it.
>I have heard it said - yep, here it is in Comer's Internetworking with
>TCP/IP, vol 1 page 415:
>
>"We think of a socket as a generalization of the UNIX file access mechanism
>that provides and endpoint for communication"
Well, as a once full-time programmer, think of Comer referring to
communication as including communication both between software inside
a single computer and between different computers.
Essentially, there are interprocess (i.e., memory) sockets and
network sockets. Both exist inside the computer. The basic
mechanism of sending to a socket is the same for both types.
When the data gets to an interprocess socket, it's already at the
program that will handle it.
Think of a network socket as the "computer side" of a particular IP
address and TCP/UDP port. Once traffic arrives there, it now has to
go through the stack of communications drivers: TCP/UDP, IP, and data
link/physical to get out of the machine.
At the other end, the traffic arrives at the data link/physical
driver, and eventually makes its way up to a network socket. The
network socket has to either already be created, or the system
software has to create one on demand. How much buffering is
associated with the socket, and where it's located, is
implementatin-specific.
>
>elsewhere ( p7 ) Comer calls a socket an abstraction that "allowed
>application programs to access communications protocols"
>
>rereading both of these sections, I see nothing that makes me want to be a
>programmer :->
>
>I can't lay my finger on it, but I recall reading someplace that in the IP
>world, the combination of IP address and TCP or UDP port is a socket
>
>I imagine the abstraction is similar for IPX, AppleTalk, and any other
>protocol suite one can name.
>
>
>
>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
>Priscilla Oppenheimer
>Sent: Wednesday, September 12, 2001 6:54 PM
>To: [EMAIL PROTECTED]
>Subject: Re: Ports and Sockets [7:19701]
>
>
>Ports are used by TCP and UDP to identify the next layer up in the packet.
>
>IP has a Protocol field that has a similar function.
>
>Ethernet II has EtherType. IEEE 802.3 has the 802.2 Service Access Point
>(SAP). IPX and AppleTalk have sockets.
>
>Almost every protocol has some way of specifying what the next layer up is.
>The recipient uses it to pass the data to the right process. The sender
>also uses it to identify itself.
>
>Socket has another meaning in the Unix world which I have never quite
>understood. Perhaps someone else can explain that.
>
>Priscilla
>
>At 08:25 PM 9/12/01, Dennis Laganiere wrote:
>>Hopefully this will start a new conversation. I've tried to describe the
>>difference between Ports and Sockets. Your thoughts are welcome...
>>
>>Port Numbers are used by IP to pass information to the upper layers; they
>>provide the mechanism for cooperating applications to communicate. Numbers
>>below 1024 are well known ports, and above 1024 are dynamically assigned
>>ports. You will usually find registered ports are for vendor specific
>>applications in the range above 1024.
>>
>>Here are some common IP Ports:
>>20/21 FTP
>>23 Telnet
>>25 SMTP
>>37 Time Service
>>49 TACACS
>>53 DNS
>>67 BootP Server
>>68 BootP Client
>>69 TFTP
>>110 POP3
>>161 SNMP
>>
>>IPX sockets are part of the IPX stack, and are used much like port numbers
>>in IP; they direct data encapsulation in the IPX Header to the appropriate
>>upper layer protocols. There are well-known ones, others that are assigned
>>to proprietary applications, and a series of numbers used randomly by
>>clients, just like in IP. Also like IP ports, they identify the process on
>>the server or client that needs to get the data in the packet.
>>
>> Here are some common IPX sockets:
> > 0x451 NCP
>> 0x452 SAP
>> 0x453 RIP
>> 0x455 NetBios
>> 0x456 Diagnostic
>> 0x457 Serialization
>> 0x85be IPX EIGRP
>> 0x9001 NLSP
>> 0x9004 IPXWAN
>> 0x9086 IPX Ping
>>
>>
>>The AppleTalk protocol suite also uses sockets. Socket numbers 1-127 are
> >statically assigned (RTMP uses 1, ZIP uses 6, etc).
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=19749&t=19701
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