TCP/IP Tutorial and Technical Overview - IBM Redbooks

The connectionless scenario is simpler in that the listen(), accept(), and
connect() functions are not invoked. Table 11-1 compares the socket API
functions that are used for connection-oriented and connectionless clients and
servers.
Table 11-1 Socket API function comparison
Client/server connection Establish Send Receive
Connection-oriented server bind()
listen()
accept()
11.2.2 Remote Procedure Call (RPC)
send()
sendto()
write()
Connection-oriented client connect() send()
sendto()
write()
recv()
recvfrom()
read()
recv()
recvfrom()
read()
Connectionless server bind() sendto() recvfrom()
Connectionless client bind() sendto() recvfrom()
Remote Procedure Call (RPC), originally developed by Sun Microsystems and
currently used by many UNIX-based systems, is an application programming
interface (API) available for developing distributed applications. It allows
programs to execute subroutines on a remote system. The caller program, which
represents the client instance in the client/server model (see Figure 11-1 on
page 409), sends a call message to the server process and waits for a reply
message. The call message includes the subroutine’s parameters, and the reply
message contains the results of executing the subroutine. RPC also provides a
standard way of encoding data passed between the client/server in a portable
fashion called External Data Representation (XDR), defined by
RFC 4506/STD 0067.
The RPC concept
The concept of RPC is very similar to that of an application program issuing a
procedure call:
1. The caller process, which represents the client instance in the client/server
model (see Figure 11-1 on page 409,) sends a call message and waits for the
reply.
2. The server awaits the arrival of call messages. When a call message arrives,
the server process extracts the procedure parameters, computes the results,
and sends them back in a reply message.
Chapter 11. Application structure and programming interfaces 415