libUV multicast例子问题

官方的例子:

TEST_IMPL(udp_multicast_join) {

  int r;

  uv_udp_send_t req;

  uv_buf_t buf;

  struct sockaddr_in addr = uv_ip4_addr("239.255.0.1", TEST_PORT);

  r = uv_udp_init(uv_default_loop(), &server);

  ASSERT(r == 0);

  r = uv_udp_init(uv_default_loop(), &client);

  ASSERT(r == 0);

  /* bind to the desired port */

  r = uv_udp_bind(&client, addr, 0);

  ASSERT(r == 0);

  /* join the multicast channel */

  r = uv_udp_set_membership(&client, "239.255.0.1", NULL, UV_JOIN_GROUP);

  ASSERT(r == 0);

  r = uv_udp_recv_start(&client, alloc_cb, cl_recv_cb);

  ASSERT(r == 0);

  buf = uv_buf_init("PING", 4);

  /* server sends "PING" */

  r = uv_udp_send(&req, &server, &buf, 1, addr, sv_send_cb);

  ASSERT(r == 0);

  ASSERT(close_cb_called == 0);

  ASSERT(cl_recv_cb_called == 0);

  ASSERT(sv_send_cb_called == 0);

  /* run the loop till all events are processed */

  uv_run(uv_default_loop());

  ASSERT(cl_recv_cb_called == 1);

  ASSERT(sv_send_cb_called == 1);

  ASSERT(close_cb_called == 2);

  return 0;

}

这段代码有个问题,multicast时本机也能收到数据.设置uv_udp_set_multicast_loop(&server, 0);也不起作用.

从代码上看,server没有bind,问题应该是出在这里.加上如下两句:

struct sockaddr_in addr2 = uv_ip4_addr("0.0.0.0", TEST_PORT+2);

uv_udp_bind(&server, addr2, 0);

再测试,本机收不到数据了.再加上uv_udp_set_multicast_loop(&server, 1) 本机又可以收到.测试环境是centos5.6,不同的环境可能表现不一样.官方写例子的时候应该是没有问题的.不过为了安全,所有的socket都bind一下好了.