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Communications in Client-Server Systems the details…
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Communications in Client-Server Systems Sockets (IPC) Remote Procedure Calls (RPC) Pipes (ordinary & named)
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Communications in Client-Server Systems Sockets - an endpoint for communication Uses TCP/IP Protocol 2 processes - 2 sockets socket identified as IP address concatenated with port number telnet: port 23 ftp: port 21 (or 22 secure) http: port 80 client calls on known port (under 1024) host establishes return port >1024 but <1625 Common/efficient low level communication unstructured stream of bytes (data) 127.0.0.1 - loopback (used when client & server are on same host)
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Communications in Client-Server Systems Remote Procedure Calls (RPC) higher level communication well structured data packet sent to a RPC daemon listening on a specific port output sent back as a separate message utilizes stub (small piece of code that indicates how to locate or load the remote library routine) External Data Representation (XDR) instead of… big-endian (most significant byte first) little-endian (least significant byte first) Implementation of call at most once (time-stamp history – ignore message with later stamp exactly once (at most once, plus ACK message from server to client)
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Communications in Client-Server Systems Pipes a conduit for two processes to communicate Higher level communication file-like (read/write) two types ordinary access within parent/child relationship of processes unidirectional two pipes are used for bi-directional communication file closed by both ends – to mark end of file end of process == end of pipe named can exist beyond a process usually more than 1 “writer” ½ duplex (UNIX) full duplex (Windows) data transmission
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