libnice simple-example 分析
编译安装
直接从git上下载源码，然后编译安装，开始遇到很多依赖问题，最后采用下载老版本的分支编译。
发起端输出
root@iZbp1bp634mlawwh9rif75Z:~/libnice-0.1.9# simple-example 0 stunserver.org
Copy this line to remote client:
qgbF 7ghYVTRnQ8xzqV7TWmC+MO 1,2013266431,172.16.99.155,35620,host 2,1019216383,172.16.99.155,0,host 3,1015022079,172.16.99.155,59862,host
Enter remote data (single line, no wrapping):
> OLi/ AAchlY0dxAJ+4RtY9YWicS 1,2013266431,172.16.99.155,53683,host 2,1019216383,172.16.99.155,0,host 3,1015022079,172.16.99.155,52272,host
Negotiation complete: ([172.16.99.155]:35620, [172.16.99.155]:53683)
Send lines to remote (Ctrl-D to quit):
> nihao被叫端输出
root@iZbp1bp634mlawwh9rif75Z:~# simple-example 1 stunserver.org
Copy this line to remote client:
OLi/ AAchlY0dxAJ+4RtY9YWicS 1,2013266431,172.16.99.155,53683,host 2,1019216383,172.16.99.155,0,host 3,1015022079,172.16.99.155,52272,host
Enter remote data (single line, no wrapping):
> qgbF 7ghYVTRnQ8xzqV7TWmC+MO 1,2013266431,172.16.99.155,35620,host 2,1019216383,172.16.99.155,0,host 3,1015022079,172.16.99.155,59862,host
Negotiation complete: ([172.16.99.155]:53683, [172.16.99.155]:35620)
Send lines to remote (Ctrl-D to quit):
> nihao源码
/*
* Copyright 2013 University of Chicago
* Contact: Bryce Allen
* Copyright 2013 Collabora Ltd.
* Contact: Youness Alaoui
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* Alternatively, the contents of this file may be used under the terms of the
* the GNU Lesser General Public License Version 2.1 (the "LGPL"), in which
* case the provisions of LGPL are applicable instead of those above. If you
* wish to allow use of your version of this file only under the terms of the
* LGPL and not to allow others to use your version of this file under the
* MPL, indicate your decision by deleting the provisions above and replace
* them with the notice and other provisions required by the LGPL. If you do
* not delete the provisions above, a recipient may use your version of this
* file under either the MPL or the LGPL.
*/
/*
* Example using libnice to negotiate a UDP connection between two clients,
* possibly on the same network or behind different NATs and/or stateful
* firewalls.
*
* Build:
* gcc -o simple-example simple-example.c `pkg-config --cflags --libs nice`
*
* Run two clients, one controlling and one controlled:
* simple-example 0 $(host -4 -t A stun.stunprotocol.org | awk '{ print $4 }')
* simple-example 1 $(host -4 -t A stun.stunprotocol.org | awk '{ print $4 }')
*/
#include 主要步骤
（1）调用nice_agent_new（）创建一个NiceAgent对象。
agent = nice_agent_new(g_main_loop_get_context (gloop),（2）设置agent的属性值（比如stun服务器的地址，端口等）
if (stun_addr) {
g_object_set(agent, "stun-server", stun_addr, NULL);
g_object_set(agent, "stun-server-port", stun_port, NULL);
}
g_object_set(agent, "controlling-mode", controlling, NULL);（3）绑定事件的回调（比如candinate收集完成）
g_signal_connect(agent, "candidate-gathering-done",
G_CALLBACK(cb_candidate_gathering_done), NULL);
g_signal_connect(agent, "new-selected-pair",
G_CALLBACK(cb_new_selected_pair), NULL);
g_signal_connect(agent, "component-state-changed",
G_CALLBACK(cb_component_state_changed), NULL);（4）调用nice_agent_add_stream创建stream
stream_id = nice_agent_add_stream(agent, 1);（5）调用nice_agent_attach_recv绑定接收到的数据
nice_agent_attach_recv(agent, stream_id, 1,
g_main_loop_get_context (gloop), cb_nice_recv, NULL);（6）调用nice_agent_gather_candidates开始收集候选candinate
if (!nice_agent_gather_candidates(agent, stream_id))
g_error("Failed to start candidate gathering");（7）本地的candinate 收集完成后会回调cb_candidate_gathering_done（），这时调用nice_agent_get_local_credentials（）和nice_agent_get_local_candidates（）可以获取candinate，ufrag及密码信息
if (!nice_agent_get_local_credentials(agent, _stream_id,
&local_ufrag, &local_password))
goto end;
cands = nice_agent_get_local_candidates(agent, _stream_id, component_id);
if (cands == NULL)
goto end;（8）拿到远端的candinate调用nice_agent_set_remote_credentials（）和nice_agent_set_remote_candidates（）告诉本地的agent
if (!nice_agent_set_remote_credentials(agent, _stream_id, ufrag, passwd)) {
g_message("failed to set remote credentials");
goto end;
}
// Note: this will trigger the start of negotiation.
if (nice_agent_set_remote_candidates(agent, _stream_id, component_id,
remote_candidates) < 1) {
g_message("failed to set remote candidates");
goto end;
}（9）调用nice_agent_send将数据发给远端的agent
if (g_io_channel_read_line (source, &line, NULL, NULL, NULL) ==
G_IO_STATUS_NORMAL) {
nice_agent_send(agent, stream_id, 1, strlen(line), line);
g_free (line);
printf("> ");
fflush (stdout);
} else {
nice_agent_send(agent, stream_id, 1, 1, "\0");
// Ctrl-D was pressed.
g_main_loop_quit (gloop);
}（附）sdp-example分析
sdp-example与simple-example基本逻辑是差不多的，主要区别是sdp-example是使用互通sdp信息来建立连接。
（10）调用nice_agent_generate_local_sdp获取sdp信息
sdp = nice_agent_generate_local_sdp (agent);
printf("Generated SDP from agent :\n%s\n\n", sdp);（11）调用nice_agent_parse_remote_sdp将远端的sdp信息设置到本地
if (sdp && nice_agent_parse_remote_sdp (agent, sdp) > 0) {
g_free (sdp);