UAC(User Agent Client) 和 UAS(User Agent Server)
SIP协议采用Client/Server模型。每一个请求(Request)触发服务器的一个操作;每个操作被称为方法(Method);每个请求除了指明具体方法外,还携带了一系列的头域(Header field),这些头域携带了各种业务信息;除了头域外,消息中还可以携带任意类型的消息体(Body),呼叫中最常使用的SDP信息就是通过消息体在Client和Server之间传递的。Server从接收到请求到处理完毕,要回复多个临时响应(Response),和一个终结响应(Response),终结响应有且只有一个。
请求和他的所有响应构成一个事务(Transaction),一个完整的呼叫过程包含多个事务,比如呼叫建立和呼叫释放就是
两个相互独立的事务。
用户代理(User Agent)是发起或者接收呼叫的逻辑实体。
用户代理客户端-UAC(User Agent Client),用于发起请求;
用户代理服务器-UAS(User Agent Server),用于接收请求。UAC/UAS的划分是针对一个事务的。在一个呼叫中的多个事务里,UAC和UAS的角色是可以互换的。例如在A和B的呼叫中,A向B发起呼叫,在呼叫建立的事务中,A是UAC,B是UAS;呼叫结束时,B先挂机,在呼叫释放的事务中,B是UAC,A是UAS。换句话说,每个一般的UA都是UAS和UAC的结合体。
UA的实际物理形态有:IP Phone,SoftPhone,GateWay......
Proxy Server作为一个网络逻辑实体代理客户端转发请求或者响应;同Proxy Server类似的还有一种设备是B2BUA,
顾名思义,就是背背的两个UA组成的一个逻辑实体,它作为UAS终结一个事务,同时作为UAC发起另外一个事务。Proxy Server同B2BUA相比,Proxy Server是一个事务传递过程中的中间节点,而B2BUA将一个事务转变成另一个事务。
在SIP组网中还包括Location Server、Registrar、Redirect Server,分别负责维护地址映射表,注册管理,呼叫重定向。他们和Proxy Server 可以在同一台设备上也可以运行于不同的设备上。SIP Server是Proxy Server、Location Server、Registrar、Redirect Server的总称。
SIP Server采用B2BUA模型。接受请求端为UAS端,代理转发或主动发起请求端为UAC端,整个SIPServr为UAC/UAS的组合体。通过UAC/UAS之间消息交互完成会话的建立、改变、结束的阶段。SIP Server协助网关交换媒体信息,
但不参与会话建立后媒体流传输。
用户代理服务器-UAS(User Agent Server),用于接收请求。UAC/UAS的划分是针对一个事务的。在一个呼叫中的多个事务里,UAC和UAS的角色是可以互换的。例如在A和B的呼叫中,A向B发起呼叫,在呼叫建立的事务中,A是UAC,B是UAS;呼叫结束时,B先挂机,在呼叫释放的事务中,B是UAC,A是UAS。换句话说,每个一般的UA都是UAS和UAC的结合体。
UA的实际物理形态有:IP Phone,SoftPhone,GateWay......
Proxy Server作为一个网络逻辑实体代理客户端转发请求或者响应;同Proxy Server类似的还有一种设备是B2BUA,
顾名思义,就是背背的两个UA组成的一个逻辑实体,它作为UAS终结一个事务,同时作为UAC发起另外一个事务。Proxy Server同B2BUA相比,Proxy Server是一个事务传递过程中的中间节点,而B2BUA将一个事务转变成另一个事务。
在SIP组网中还包括Location Server、Registrar、Redirect Server,分别负责维护地址映射表,注册管理,呼叫重定向。他们和Proxy Server 可以在同一台设备上也可以运行于不同的设备上。SIP Server是Proxy Server、Location Server、Registrar、Redirect Server的总称。
SIP Server采用B2BUA模型。接受请求端为UAS端,代理转发或主动发起请求端为UAC端,整个SIPServr为UAC/UAS的组合体。通过UAC/UAS之间消息交互完成会话的建立、改变、结束的阶段。SIP Server协助网关交换媒体信息,
但不参与会话建立后媒体流传输。
代码 uac.c
#include <eXosip2/eXosip.h> #include <stdio.h> #include <stdlib.h> #include <stdarg.h> #include <netinet/in.h> //#include <winsock2.h> int main(int argc,char *argv[]) { struct eXosip_t *context_eXosip; eXosip_event_t *je; osip_message_t *reg=NULL; osip_message_t *invite=NULL; osip_message_t *ack=NULL; osip_message_t *info=NULL; osip_message_t *message=NULL; int call_id,dialog_id; int i,flag; int flag1=1; char *identity="sip:140@127.0.0.1"; //UAC1,端口是15060 char *registar="sip:133@127.0.0.1:15061"; //UAS,端口是15061 char *source_call="sip:140@127.0.0.1"; char *dest_call="sip:133@127.0.0.1:15061"; //identify和register这一组地址是和source和destination地址相同的 //在这个例子中,uac和uas通信,则source就是自己的地址,而目的地址就是uac1的地址 char command; char tmp[4096]; printf("r 向服务器注册 "); printf("c 取消注册 "); printf("i 发起呼叫请求 "); printf("h 挂断 "); printf("q 推出程序 "); printf("s 执行方法INFO "); printf("m 执行方法MESSAGE "); //初始化 i=eXosip_init(); if(i!=0) { printf("Couldn't initialize eXosip! "); return -1; } else { printf("eXosip_init successfully! "); } //绑定uac自己的端口15060,并进行端口监听 i=eXosip_listen_addr(IPPROTO_UDP,NULL,15060,AF_INET,0); if(i!=0) { eXosip_quit(); fprintf(stderr,"Couldn't initialize transport layer! "); return -1; } flag=1; while(flag) { //输入命令 printf("Please input the command: "); scanf("%c",&command); getchar(); switch(command) { case 'r': printf("This modal is not completed! "); break; case 'i'://INVITE,发起呼叫请求 i=eXosip_call_build_initial_invite(&invite,dest_call,source_call,NULL,"This is a call for conversation"); if(i!=0) { printf("Initial INVITE failed! "); break; } //符合SDP格式,其中属性a是自定义格式,也就是说可以存放自己的信息, //但是只能有两列,比如帐户信息 //但是经过测试,格式vot必不可少,原因未知,估计是协议栈在传输时需要检查的 snprintf(tmp,4096, "v=0 " "o=anonymous 0 0 IN IP4 0.0.0.0 " "t=1 10 " "a=username:rainfish " "a=password:123 "); osip_message_set_body(invite,tmp,strlen(tmp)); osip_message_set_content_type(invite,"application/sdp"); eXosip_lock(); i=eXosip_call_send_initial_invite(invite); //invite SIP INVITE message to send eXosip_unlock(); //发送了INVITE消息,等待应答 flag1=1; while(flag1) { je=eXosip_event_wait(0,200); //Wait for an eXosip event //(超时时间秒,超时时间毫秒) if(je==NULL) { printf("No response or the time is over! "); break; } switch(je->type) //可能会到来的事件类型 { case EXOSIP_CALL_INVITE: //收到一个INVITE请求 printf("a new invite received! "); break; case EXOSIP_CALL_PROCEEDING: //收到100 trying消息,表示请求正在处理中 printf("proceeding! "); break; case EXOSIP_CALL_RINGING: //收到180 Ringing应答,表示接收到INVITE请求的UAS正在向被叫用户振铃 printf("ringing! "); printf("call_id is %d,dialog_id is %d ",je->cid,je->did); break; case EXOSIP_CALL_ANSWERED: //收到200 OK,表示请求已经被成功接受,用户应答 printf("ok!connected! "); call_id=je->cid; dialog_id=je->did; printf("call_id is %d,dialog_id is %d ",je->cid,je->did); //回送ack应答消息 eXosip_call_build_ack(je->did,&ack); eXosip_call_send_ack(je->did,ack); flag1=0; //推出While循环 break; case EXOSIP_CALL_CLOSED: //a BYE was received for this call printf("the other sid closed! "); break; case EXOSIP_CALL_ACK: //ACK received with 200ok to INVITE (就是发送INVITE后,收到了对该INVITE的ACK) printf("ACK received! "); break; default: //收到其他应答 printf("other response! "); break; } eXosip_event_free(je); //Free ressource in an eXosip event } break; case 'h': //挂断 printf("Holded! "); eXosip_lock(); eXosip_call_terminate(call_id,dialog_id); eXosip_unlock(); break; case 'c': printf("This modal is not commpleted! "); break; case 's': //传输INFO方法 eXosip_call_build_info(dialog_id,&info); snprintf(tmp,4096," This is a sip message(Method:INFO)"); osip_message_set_body(info,tmp,strlen(tmp)); //格式可以任意设定,text/plain代表文本信息; osip_message_set_content_type(info,"text/plain"); eXosip_call_send_request(dialog_id,info); break; case 'm': //传输MESSAGE方法,也就是即时消息,和INFO方法相比,我认为主要区别是: //MESSAGE不用建立连接,直接传输信息,而INFO消息必须在建立INVITE的基础上传输 printf("the method : MESSAGE "); eXosip_message_build_request(&message,"MESSAGE",dest_call,source_call,NULL); //内容,方法, to ,from ,route snprintf(tmp,4096,"This is a sip message(Method:MESSAGE)"); osip_message_set_body(message,tmp,strlen(tmp)); //假设格式是xml osip_message_set_content_type(message,"text/xml"); eXosip_message_send_request(message); break; case 'q': eXosip_quit(); printf("Exit the setup! "); flag=0; break; } } return(0); }
代码 uas.c
# include <eXosip2/eXosip.h> # include <stdio.h> # include <stdlib.h> # include <stdarg.h> # include <netinet/in.h> //# include <Winsock2.h> int main (int argc, char *argv[]) { eXosip_event_t *je = NULL; osip_message_t *ack = NULL; osip_message_t *invite = NULL; osip_message_t *answer = NULL; sdp_message_t *remote_sdp = NULL; int call_id, dialog_id; int i,j; int id; char *sour_call = "sip:140@127.0.0.1"; char *dest_call = "sip:133@127.0.0.1:15060";//client ip char command; char tmp[4096]; char localip[128]; int pos = 0; //初始化sip i = eXosip_init (); if (i != 0) { printf ("Can't initialize eXosip! "); return -1; } else { printf ("eXosip_init successfully! "); } i = eXosip_listen_addr (IPPROTO_UDP, NULL, 15061, AF_INET, 0); if (i != 0) { eXosip_quit (); fprintf (stderr, "eXosip_listen_addr error! Couldn't initialize transport layer! "); } for(;;) { //侦听是否有消息到来 je = eXosip_event_wait (0,50); //协议栈带有此语句,具体作用未知 eXosip_lock (); eXosip_default_action (je); eXosip_automatic_refresh (); eXosip_unlock (); if (je == NULL)//没有接收到消息 continue; // printf ("the cid is %s, did is %s/n", je->did, je->cid); switch (je->type) { case EXOSIP_MESSAGE_NEW://新的消息到来 printf (" EXOSIP_MESSAGE_NEW! "); if (MSG_IS_MESSAGE (je->request))//如果接受到的消息类型是MESSAGE { { osip_body_t *body; osip_message_get_body (je->request, 0, &body); printf ("I get the msg is: %s ", body->body); //printf ("the cid is %s, did is %s/n", je->did, je->cid); } //按照规则,需要回复OK信息 eXosip_message_build_answer (je->tid, 200,&answer); eXosip_message_send_answer (je->tid, 200,answer); } break; case EXOSIP_CALL_INVITE: //得到接收到消息的具体信息 printf ("Received a INVITE msg from %s:%s, UserName is %s, password is %s ",je->request->req_uri->host, je->request->req_uri->port, je->request->req_uri->username, je->request->req_uri->password); //得到消息体,认为该消息就是SDP格式. remote_sdp = eXosip_get_remote_sdp (je->did); call_id = je->cid; dialog_id = je->did; eXosip_lock (); eXosip_call_send_answer (je->tid, 180, NULL); i = eXosip_call_build_answer (je->tid, 200, &answer); if (i != 0) { printf ("This request msg is invalid!Cann't response! "); eXosip_call_send_answer (je->tid, 400, NULL); } else { snprintf (tmp, 4096, "v=0 " "o=anonymous 0 0 IN IP4 0.0.0.0 " "t=1 10 " "a=username:rainfish " "a=password:123 "); //设置回复的SDP消息体,下一步计划分析消息体 //没有分析消息体,直接回复原来的消息,这一块做的不好。 osip_message_set_body (answer, tmp, strlen(tmp)); osip_message_set_content_type (answer, "application/sdp"); eXosip_call_send_answer (je->tid, 200, answer); printf ("send 200 over! "); } eXosip_unlock (); //显示出在sdp消息体中的attribute 的内容,里面计划存放我们的信息 printf ("the INFO is : "); while (!osip_list_eol ( &(remote_sdp->a_attributes), pos)) { sdp_attribute_t *at; at = (sdp_attribute_t *) osip_list_get ( &remote_sdp->a_attributes, pos); printf ("%s : %s ", at->a_att_field, at->a_att_value);//这里解释了为什么在SDP消息体中属性a里面存放必须是两列 pos ++; } break; case EXOSIP_CALL_ACK: printf ("ACK recieved! "); // printf ("the cid is %s, did is %s/n", je->did, je->cid); break; case EXOSIP_CALL_CLOSED: printf ("the remote hold the session! "); // eXosip_call_build_ack(dialog_id, &ack); //eXosip_call_send_ack(dialog_id, ack); i = eXosip_call_build_answer (je->tid, 200, &answer); if (i != 0) { printf ("This request msg is invalid!Cann't response! "); eXosip_call_send_answer (je->tid, 400, NULL); } else { eXosip_call_send_answer (je->tid, 200, answer); printf ("bye send 200 over! "); } break; case EXOSIP_CALL_MESSAGE_NEW://至于该类型和EXOSIP_MESSAGE_NEW的区别,源代码这么解释的 /* // request related events within calls (except INVITE) EXOSIP_CALL_MESSAGE_NEW, < announce new incoming request. // response received for request outside calls EXOSIP_MESSAGE_NEW, < announce new incoming request. 我也不是很明白,理解是:EXOSIP_CALL_MESSAGE_NEW是一个呼叫中的新的消息到来,比如ring trying都算,所以在接受到后必须判断 该消息类型,EXOSIP_MESSAGE_NEW而是表示不是呼叫内的消息到来。 该解释有不妥地方,仅供参考。 */ printf(" EXOSIP_CALL_MESSAGE_NEW "); if (MSG_IS_INFO(je->request) ) //如果传输的是INFO方法 { eXosip_lock (); i = eXosip_call_build_answer (je->tid, 200, &answer); if (i == 0) { eXosip_call_send_answer (je->tid, 200, answer); } eXosip_unlock (); { osip_body_t *body; osip_message_get_body (je->request, 0, &body); printf ("the body is %s ", body->body); } } break; default: printf ("Could not parse the msg! "); } } }