tcp_send(+Socket, +Term)

This sends Term to the process whose socket identifier is Socket. Socket gets the term term(From,Term) from tcp_select/[1,2] (see ipc-tcp-trm-select1).

Note that tcp_send/2 can only be used to send terms to a Prolog server as Term is sent in an encoded form that is efficiently decoded by tcp_select/[1,2] (see ipc-tcp-trm-select1).

Here is an example of how one might use tcp_send/2 to implement a remote procedure call to some process whose file descriptor is P. It is assumed that the connections between the two processes have been established elsewhere.

     :-use_module(library(basics), [member/2]).
     :-use_module(library(freevars), [free_variables/4]).
     % machine a has p_call/2
     p_call(P, Goal):-
         free_variables(Goal, [], [], FreeVars),
         tcp_send(P, satisfy(FreeVars, Goal)),
         tcp_select(term(P, Bag)),
         member(FreeVars, Bag).
     % machine b has slave/0
         T = term(P, satisfy(FreeVars, Goal)),
             findall(FreeVars, Goal, Bag),
             tcp_send(P, Bag),

The use of library(freevars) is to limit the amount of data being sent by the slave to just those variables that may be instantiated by calling Goal.

For many applications this is all that is required. It has the advantage of limiting both the frequency of messages sent (findall/3), and the size of the messages (free_variables/4). A better implementation of remote procedure call would allow the caller to respond to solutions from several different machines as soon as the solutions are generated, without waiting for the solutions to be assembled into a list. This is attempted in the example program IPC/TCP/demo/ (see ipc-tcp-exa).

If you try to send to a broken socket, the "Broken pipe" exception is raised: