CNode指南

1   概述

利用Erlang的 erl_interface ,我们可以构建自己的Erlang “Node”,我们称为 “CNode “,erl_interface实现了基本的节点连接,以及消息发送接收,以及Erlang Term 的构建解析.

使用CNode,可以完成很多使用port完成的功能,区别是你的应用是一个c程序,而不需要 一个erlang应用.

CNode是hidden node,在erlang的 nodes() 结果中,无法看到CNode(可以通过nodes(connected)获取)

2   CNode 相关API

while (loop) { got = erl_receive_msg(fd, buf, BUFSIZE, &emsg); if (got == ERL_TICK) { /* ignore */ } else if (got == ERL_ERROR) { loop = 0; /* exit while loop */ } else { if (emsg.type == ERL_REG_SEND) { 

fromp = erl_element(2, emsg.msg); tuplep = erl_element(3, emsg.msg); fnp = erl_element(1, tuplep); argp = erl_element(2, tuplep); if (strncmp(ERL_ATOM_PTR(fnp), "foo", 3) == 0) { res = foo(ERL_INT_VALUE(argp)); } else if (strncmp(ERL_ATOM_PTR(fnp), "bar", 3) == 0) { res = bar(ERL_INT_VALUE(argp)); } 

erl_free_term(emsg.from); erl_free_term(emsg.msg); erl_free_term(fromp); erl_free_term(tuplep); erl_free_term(fnp); erl_free_term(argp); erl_free_term(resp); resp = erl_format("{cnode, ~i}", res); erl_send(fd, fromp, resp); 

-module(complex3). -export([foo/1, bar/1]). foo(X) -> call_cnode({foo, X}). bar(Y) -> call_cnode({bar, Y}). call_cnode(Msg) -> {any, c1@litao} ! {call, self(), Msg}, receive {cnode, Result} -> Result end. 

3   编译运行

编译C node:

$ gcc -o cserver -I/usr/local/lib/erlang/lib/erl_interface-3.6.2/include \ -L/usr/local/lib/erlang/lib/erl_interface-3.6.2/lib \ complex.c cnode_s.c -g -rdynamic -lerl_interface -lei -lnsl -lpthread 

启动epmd:

epmd -d -d #以debug方式启动 

启动cserver:

./cserver 2342 

至此C node启动完成，其绑定的本地端口为2342

启动client:

erl -sname t1 

设置 c1@litao 的cookie，连接c1节点:

(t1@litao)6> erlang:set_cookie('c1@litao', 'secretcookie'). true (t1@litao)7> net_kernel:connect_node('c1@litao'). true (t1@litao)8> nodes(connected). [c1@litao] 

执行调用:

(t1@litao)12> complex3:foo(3). 4 

4   完整代码

cnode_s.c:

/* cnode_s.c */ #include <stdio.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include "erl_interface.h" #include "ei.h" #define BUFSIZE 1000 int main(int argc, char argv) { int port; /* Listen port number */ int listen; /* Listen socket */ int fd; /* fd to Erlang node */ ErlConnect conn; /* Connection data */ int loop = 1; /* Loop flag */ int got; /* Result of receive */ unsigned char buf[BUFSIZE]; /* Buffer for incoming message */ ErlMessage emsg; /* Incoming message */ ETERM *fromp, *tuplep, *fnp, *argp, *resp; int res; port = atoi(argv[1]); erl_init(NULL, 0); if (erl_connect_init(1, "secretcookie", 0) == -1) erl_err_quit("erl_connect_init"); /* Make a listen socket */ if ((listen = my_listen(port)) <= 0) erl_err_quit("my_listen"); if (erl_publish(port) == -1) erl_err_quit("erl_publish"); if ((fd = erl_accept(listen, &conn)) == ERL_ERROR) erl_err_quit("erl_accept"); fprintf(stderr, "Connected to %s\n\r", conn.nodename); while (loop) { got = erl_receive_msg(fd, buf, BUFSIZE, &emsg); if (got == ERL_TICK) { /* ignore */ } else if (got == ERL_ERROR) { loop = 0; } else { if (emsg.type == ERL_REG_SEND) { fromp = erl_element(2, emsg.msg); tuplep = erl_element(3, emsg.msg); fnp = erl_element(1, tuplep); argp = erl_element(2, tuplep); if (strncmp(ERL_ATOM_PTR(fnp), "foo", 3) == 0) { res = foo(ERL_INT_VALUE(argp)); } else if (strncmp(ERL_ATOM_PTR(fnp), "bar", 3) == 0) { res = bar(ERL_INT_VALUE(argp)); } resp = erl_format("{cnode, ~i}", res); erl_send(fd, fromp, resp); erl_free_term(emsg.from); erl_free_term(emsg.msg); erl_free_term(fromp); erl_free_term(tuplep); erl_free_term(fnp); erl_free_term(argp); erl_free_term(resp); } } } /* while */ } int my_listen(int port) { int listen_fd; struct sockaddr_in addr; int on = 1; if ((listen_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) return (-1); setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)); memset((void*) &addr, 0, (size_t) sizeof(addr)); addr.sin_family = AF_INET; addr.sin_port = htons(port); addr.sin_addr.s_addr = htonl(INADDR_ANY); if (bind(listen_fd, (struct sockaddr*) &addr, sizeof(addr)) < 0) return (-1); listen(listen_fd, 5); return listen_fd; } 

compex.c:

/* complex.c */ int foo(int x) { return x+1; } int bar(int y) { return y*2; }