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@Florida

Thank you very much for the enlightening reply! However, I think the IP address is more like the telephone number in the telebanking. After doing some readings, my understanding is:

letstalk(e only)
本文发表在 rolia.net 枫下论坛1. Server and Client keep the identical list of RPC service numbers; (originally defined by SUN)
2. Server can dynamically (non-universally) assign port numbers above 1024 to RPC services. Port 111 (or 135 in Microsoft OS) is specifically for portmap / rpcbind service.
3. Client uses RPC service number, instead of service name or port number, to call Server for a RCP service;
4. Server’s portmap/rpcbind use the RPC service number to find the port number and return to Client;
5. Client then use the port number to call xinetd/inetd daemon for the service;
6. xinetd/inetd daemon start the service;The service communicates with the client.

One goal behind the development of the remote procedure call (RPC) protocol was to build a solution for the limited number of service ports available in the TCP and UDP protocols. In both TCP and UDP, ports are defined in a 2-byte field, which limits the number of ports to 65,536.
Instead of using static service-port mappings, RPC provides a dynamic service-port mapping function. In RPC, incoming RPC calls are mapped to a variable port in the 1024 to 65,535 range. Although RPC uses variable service ports, it needs a unique way to identify services. The RPC protocol resolves this need by using a special service identifier and a dedicated Portmapper service. The unique RPC identifier is called the RPC service number. Service numbers are defined in a 4-byte field, which provides up to 4,294,967,296 possible service numbers. The Portmapper service listens on a static port (TCP or UDP port 135 in Windows or 111 in Unix/Linux). The service exists primarily to map the unique RPC service number on a variable TCP/UDP port. Thus, RPC can provide both a unique way to identify RPC services and a way to dynamically allocate the scarce number of TCP/UDP service ports. . . .更多精彩文章及讨论，请光临枫下论坛 rolia.net
(#4542008@0)
Last Updated: 2008-7-7
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Replies, comments and Discussions:

  • 工作学习 / 学科技术讨论 / 那位能简明说一下，RPC (or portmapper) 是怎样利用RPC service number的吗? 既然已经有了port number了，比如说23 for telnet，为什么还用service number呢？谢谢。 -letstalk(e only); 2008-6-11 (#4496477@0)
    • Anyone, please? -letstalk(e only); 2008-6-12 (#4498315@0)
    • RPC is a protocol on top of TCP/IP -diresu(makeITwork); 2008-7-4 {702} (#4537299@0)
      or simply use TCP as transport. Port, IMO, is just a English word refers the interface between host system and guest system. In comparison with the tele-banking, TCP port # is the telephone number, RPC port # is your bank service code such as "press 1 for account balance". You have to dial the bank phone (connect TCP port 135/RPC directory first), wait for instruction (RPC response), then listen to the instruction and find out dial service code (RPC #). You may required to dial a different # (other TCP port) or come to the counter or ATM (RPC over shared memory or other IPC). If there is common thing between service code and phone #, it is that they all number of digits. Same to the port #s.
      • Thank you very much for the enlightening reply! However, I think the IP address is more like the telephone number in the telebanking. After doing some readings, my understanding is: -letstalk(e only); 2008-7-7 {1831} (#4542008@0)
        本文发表在 rolia.net 枫下论坛1. Server and Client keep the identical list of RPC service numbers; (originally defined by SUN)
        2. Server can dynamically (non-universally) assign port numbers above 1024 to RPC services. Port 111 (or 135 in Microsoft OS) is specifically for portmap / rpcbind service.
        3. Client uses RPC service number, instead of service name or port number, to call Server for a RCP service;
        4. Server’s portmap/rpcbind use the RPC service number to find the port number and return to Client;
        5. Client then use the port number to call xinetd/inetd daemon for the service;
        6. xinetd/inetd daemon start the service;The service communicates with the client.

        One goal behind the development of the remote procedure call (RPC) protocol was to build a solution for the limited number of service ports available in the TCP and UDP protocols. In both TCP and UDP, ports are defined in a 2-byte field, which limits the number of ports to 65,536.
        Instead of using static service-port mappings, RPC provides a dynamic service-port mapping function. In RPC, incoming RPC calls are mapped to a variable port in the 1024 to 65,535 range. Although RPC uses variable service ports, it needs a unique way to identify services. The RPC protocol resolves this need by using a special service identifier and a dedicated Portmapper service. The unique RPC identifier is called the RPC service number. Service numbers are defined in a 4-byte field, which provides up to 4,294,967,296 possible service numbers. The Portmapper service listens on a static port (TCP or UDP port 135 in Windows or 111 in Unix/Linux). The service exists primarily to map the unique RPC service number on a variable TCP/UDP port. Thus, RPC can provide both a unique way to identify RPC services and a way to dynamically allocate the scarce number of TCP/UDP service ports. . . .更多精彩文章及讨论，请光临枫下论坛 rolia.net
    • 跟inetd差不多，比inetd高级，应用接口要有stub什么的。再高级一点就IIOP,SOAP了。 -647i(流浪的步行万里); 2008-7-5 (#4539128@0)

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