【p2p、分布式，区块链笔记 UPNP】: 简单服务发现协议 SSDP

server/2024/10/23 17:13:39/
  • 在设备加入网络，UPnP发现协议允许设备向控制点广告它的服务。它使用向一个标准地址和端口多址传送发现消息来实现。控制点在此端口上侦听是否有新服务加入系统。为了通知所有设备，一个设备为每个其上的嵌入设备和服务发送一系列相应的发现消息。每个消息也包含它表征设备或服务的特定信息。

SSDP的数据内容格式

  • SSDP (Simple Service Discovery Protocol) 的数据内容格式与HTTP协议格式十分类似。SSDP是一种基于 HTTPU (HTTP over UDP) 的协议，通常用于 UPnP 设备发现。

  • 注：HTTP（HyperText Transfer Protocol）属于计算机网络中的应用层协议。而TCP/UDP是传输层协议。HTTP只是定义了一种信息的描述格式，并不一定要使用TCP进行传输。

  • SSDP是一种基于 UDP 的协议，所以它并不涉及到TCP协议中的三次握手（three-way handshake）来建立连接或者四次挥手（four-segment handshake）来关闭连接。

  • SSDP的操作主要包括发送发现请求（M-SEARCH）、响应发现请求（NOTIFY）以及注册服务（NOTIFY + LOCATION）等操作。它的工作机制主要是基于广播和多播消息，用于通告服务的存在以及查询网络上的服务。

特性广播 (Broadcast)多播 (Multicast)
目标主机网络中的所有主机特定的一组主机
地址范围255.255.255.255 (IPv4)224.0.0.0 到 239.255.255.255 (IPv4)
传输范围局域网 (LAN)局域网 (LAN) 和广域网 (WAN)
网络负载高，因为所有设备都会接收低，因为只有需要的设备接收
使用场景ARP、DHCP 等简单网络服务视频流、股票行情、在线游戏等
跨网络传输不能跨路由器传播可以跨路由器传播（需配置）
带宽效率低，所有主机都接收高，只有订阅的主机接收
  • 在IPv4环境，当需要使用多播方式传送相关消息的时候，SSDP一般使用多播地址239.255.255.250和UDP端口号1900。

设备和控制点在SSDP中的角色

  • 设备（Device）：
    • 被发现的设备，通常是嵌入式设备或网络设备。设备会周期性地发送NOTIFY消息来广播自己的存在。
    • 当收到M-SEARCH请求时，也会响应NOTIFY消息。
  • 控制点（Control Point）：
    • 发起服务发现的客户端，通常是PC、手机等。
    • 控制点通过发送M-SEARCH请求来寻找特定的服务。
    • 接收到NOTIFY消息后，控制点就可以对设备进行控制或获取信息。

NOTIFY报文

  • 当设备通过DHCP或其他方式获取IP并加入网络后，会同构239.255.255.250:1900进行多播通告，控制点监听此端口以发现新的服务。
/*!* \brief Sends SSDP advertisements, replies and shutdown messages.** \return UPNP_E_SUCCESS if successful else appropriate error.*/
int AdvertiseAndReply(/* [in] -1 = Send shutdown, 0 = send reply, 1 = Send Advertisement. */int AdFlag,/* [in] Device handle. int  value  return by UpnpRegisterRootDevice、 UpnpRegisterRootDevice2、UpnpRegisterRootDevice3 or  UpnpRegisterRootDevice4*/UpnpDevice_Handle Hnd, /* [in] Search type for sending replies. */enum SsdpSearchType SearchType,/* [in] Destination address. */struct sockaddr *DestAddr,/* [in] Device type. */char *DeviceType,/* [in] Device UDN. <UDN>uuid:UUID</UDN>  */char *DeviceUDN,/* [in] Service type. */char *ServiceType,/* [in] Advertisement age. */int Exp);

ssdp:alive

2024-10-05 19:39:29 UPNP-SSDP-2: Thread:0x7F5331C176C0 [.upnp/src/ssdp/ssdp_server.c:878]: Start of received response ----------------------------------------------------
NOTIFY * HTTP/1.1
HOST: 239.255.255.250:1900
CACHE-CONTROL: max-age=100
LOCATION: http://192.168.19.70:49152/tvdevicedesc.xml
OPT: "http://schemas.upnp.org/upnp/1/0/"; ns=01
01-NLS: 3f8c3c84-830e-11ef-b9c9-a0de7ba280b6
NT: urn:schemas-upnp-org:service:tvpicture:1 # 服务类型    
NTS: ssdp:alive  #表示通知消息的子类型
SERVER: Linux/5.15.153.1-microsoft-standard-WSL2, UPnP/1.0, Portable SDK for UPnP devices/17.2.0
X-User-Agent: redsonic
USN: uuid:Upnp-TVEmulator-1_0-1234567890001::urn:schemas-upnp-org:service:tvpicture:1End of received response ------------------------------------------------------
From host 192.168.19.70
  • 各字段描述见UPnP-arch-DeviceArchitecture-v1.0.pdf的16页。

ssdp:byebye

NOTIFY * HTTP/1.1Host: 239.255.255.250:reservedSSDPportNT: someunique:idscheme3NTS: ssdp:byebyeUSN: someunique:idscheme3

SEARCH报文

  • 控制点向网络广播一个M-SEARCH请求(ssdp:discover)。请求中包含了目标的服务类型。

ssdp:discover

M-SEARCH * HTTP/1.1S: uuid:ijklmnop-7dec-11d0-a765-00a0c91e6bf6Host: 239.255.255.250:reservedSSDPportMan: "ssdp:discover"ST: ssdp:all  # 查询的目标MX: 3HTTP/1.1 200 OKS: uuid:ijklmnop-7dec-11d0-a765-00a0c91e6bf6Ext:Cache-Control: no-cache="Ext", max-age = 5000ST: ge:fridgeUSN: uuid:abcdefgh-7dec-11d0-a765-00a0c91e6bf6AL: <blender:ixl><http://foo/bar>

响应消息 (Response)

  • 当设备接收到 M-SEARCH 消息时，如果匹配，会发送一个响应消息来通知请求者设备或服务的存在。控制点接收到NOTIFY消息后，就可以根据设备提供的详细信息，与设备建立连接。
HTTP/1.1 200 OK # 表示成功响应
CACHE-CONTROL: max-age=1800 # 指定响应的有效时间，以秒为单位
DATE: Tue, 20 Oct 2024 10:24:00 GMT # 响应生成的时间戳
EXT:  # 扩展字段，保持空白
LOCATION: http://192.168.1.100:80/upnp/device.xml # 设备的 UPnP 描述文件的 URL 
SERVER: Linux/2.6 UPnP/1.0 MediaTomb/0.12 # 包含设备的操作系统、UPnP 版本以及产品信息
ST: urn:schemas-upnp-org:device:MediaServer:1 # 搜索目标，响应请求中指定的设备或服务类型。
USN: uuid:abcd1234-5678-90ab-cdef-1234567890ab::urn:schemas-upnp-org:device:MediaServer:1 #  唯一服务名称，通常由设备的 UUID 和服务类型组成

代码实现

ST SsdpSearchType

// upnp\src\inc\ssdplib.h#L66-L75
/*! Enumeration to define all different types of ssdp searches */
typedef enum SsdpSearchType
{/*! Unknown search command. */SSDP_SERROR = -1,SSDP_ALL,SSDP_ROOTDEVICE,SSDP_DEVICEUDN,SSDP_DEVICETYPE,SSDP_SERVICE
} SType;

// upnp\src\inc\ssdplib.h#L77-L84
#define BUFSIZE (size_t)2500
#define SSDP_IP "239.255.255.250"
#define SSDP_IPV6_LINKLOCAL "FF02::C"
#define SSDP_IPV6_SITELOCAL "FF05::C"
#define SSDP_PORT 1900
#define NUM_TRY 3
#define THREAD_LIMIT 50
#define COMMAND_LEN 300

AdvertiseAndReply函数

// pupnp-branch-1.14.x\upnp\src\ssdp\ssdp_server.c
/*!* \brief 发送 SSDP 广告、回复和关闭消息。** \return 如果成功返回 UPNP_E_SUCCESS，否则返回适当的错误码。*/
int AdvertiseAndReply(int AdFlag,           /* [in] -1 = 发送关闭消息，0 = 发送回复，1 = 发送广告。 */UpnpDevice_Handle Hnd,/* [in] 设备句柄。 */enum SsdpSearchType SearchType, /* [in] 发送回复的搜索类型。 */struct sockaddr *DestAddr, /* [in] 目标地址。 */char *DeviceType,    /* [in] 设备类型。 */char *DeviceUDN,     /* [in] 设备 UDN。 */char *ServiceType,   /* [in] 服务类型。 */int Exp              /* [in] 广告有效期。 */
)
{// 初始化了一些变量int retVal = UPNP_E_SUCCESS; long unsigned int i; long unsigned int j;	int defaultExp = DEFAULT_MAXAGE;	struct Handle_Info *SInfo = NULL;	char UDNstr[100];	char devType[100];	char servType[100];	IXML_NodeList *nodeList = NULL;	IXML_NodeList *tmpNodeList = NULL;	IXML_Node *tmpNode = NULL;	IXML_Node *tmpNode2 = NULL;	IXML_Node *textNode = NULL;	const DOMString tmpStr;	const DOMString dbgStr;	int NumCopy = 0;memset(UDNstr, 0, sizeof(UDNstr));	memset(devType, 0, sizeof(devType));	memset(servType, 0, sizeof(servType));UpnpPrintf(UPNP_ALL,API,__FILE__,__LINE__,"Inside AdvertiseAndReply with AdFlag = %d\n",AdFlag);/* Use a read lock */HandleReadLock(); // 检查设备句柄的有效性。如果句柄无效，则返回错误。if (GetHandleInfo(Hnd, &SInfo) != HND_DEVICE) {retVal = UPNP_E_INVALID_HANDLE;		goto end_function;	}defaultExp = SInfo->MaxAge;/* parse the device list and send advertisements/replies */while (NumCopy == 0 || (AdFlag && NumCopy < NUM_SSDP_COPY)) {// 资源解析，一般如果发生错误，continue跳过后续步骤，进入下一次循环过程if (NumCopy != 0)imillisleep(SSDP_PAUSE);NumCopy++;for (i = 0lu;; i++) {UpnpPrintf(UPNP_ALL,API,__FILE__,__LINE__,"Entering new device list with i = %lu\n\n",	i);tmpNode = ixmlNodeList_item(SInfo->DeviceList, i);if (!tmpNode) {UpnpPrintf(UPNP_ALL,API,__FILE__,__LINE__,"Exiting new device list with i = "       "%lu\n\n",i);break;}dbgStr = ixmlNode_getNodeName(tmpNode);UpnpPrintf(UPNP_INFO,API,__FILE__,	__LINE__,"Extracting device type once for %s\n",dbgStr);ixmlNodeList_free(nodeList);nodeList = ixmlElement_getElementsByTagName((IXML_Element *)tmpNode, "deviceType");if (!nodeList) continue;UpnpPrintf(UPNP_ALL,API,__FILE__,__LINE__,"Extracting UDN for %s\n",dbgStr);UpnpPrintf(UPNP_ALL,API,__FILE__,__LINE__,"Extracting device type\n");tmpNode2 = ixmlNodeList_item(nodeList, 0lu);if (!tmpNode2) continue;textNode = ixmlNode_getFirstChild(tmpNode2);if (!textNode) continue;UpnpPrintf(UPNP_ALL,API,__FILE__,__LINE__,"Extracting device type \n");tmpStr = ixmlNode_getNodeValue(textNode);if (!tmpStr) continue;strncpy(devType, tmpStr, sizeof(devType) - 1);UpnpPrintf(UPNP_ALL,API,__FILE__,__LINE__,"Extracting device type = %s\n",				devType);if (!tmpNode) { UpnpPrintf(UPNP_ALL,	API,__FILE__,	__LINE__,"TempNode is NULL\n");	}dbgStr = ixmlNode_getNodeName(tmpNode);UpnpPrintf(UPNP_ALL,API,__FILE__,__LINE__,"Extracting UDN for %s\n",dbgStr);ixmlNodeList_free(nodeList);nodeList = ixmlElement_getElementsByTagName((IXML_Element *)tmpNode, "UDN");if (!nodeList) {UpnpPrintf(UPNP_CRITICAL,API,__FILE__,	__LINE__,"UDN not found!\n");continue;}tmpNode2 = ixmlNodeList_item(nodeList, 0lu);if (!tmpNode2) {UpnpPrintf(UPNP_CRITICAL,API,__FILE__,	__LINE__,"UDN not found!\n");continue;}textNode = ixmlNode_getFirstChild(tmpNode2);if (!textNode) {UpnpPrintf(UPNP_CRITICAL,API,__FILE__,__LINE__,"UDN not found!\n");continue;}tmpStr = ixmlNode_getNodeValue(textNode);if (!tmpStr) {UpnpPrintf(UPNP_CRITICAL,API,__FILE__,__LINE__,"UDN not found!\n");	continue;}strncpy(UDNstr, tmpStr, sizeof(UDNstr) - 1);UpnpPrintf(UPNP_INFO,API,__FILE__,__LINE__,"Sending UDNStr = %s \n",UDNstr);if (AdFlag) {/* send the device advertisement */if (AdFlag == 1) {DeviceAdvertisement(devType,i == 0lu,UDNstr,SInfo->DescURL,	Exp,SInfo->DeviceAf,SInfo->PowerState,SInfo->SleepPeriod,SInfo->RegistrationState);} else {/* AdFlag == -1 */DeviceShutdown(devType,	i == 0lu,UDNstr,	SInfo->DescURL,	Exp,SInfo->DeviceAf,SInfo->PowerState,SInfo->SleepPeriod,SInfo->RegistrationState);}} else {switch (SearchType) {case SSDP_ALL:DeviceReply(DestAddr,devType,i == 0lu,UDNstr,SInfo->DescURL,defaultExp,SInfo->PowerState,SInfo->SleepPeriod,SInfo->RegistrationState);break;case SSDP_ROOTDEVICE:if (i == 0lu) {SendReply(DestAddr,devType,1,UDNstr,SInfo->DescURL,defaultExp,0,SInfo->PowerState,SInfo->SleepPeriod,SInfo->RegistrationState);}break;case SSDP_DEVICEUDN: {/* clang-format off */if (DeviceUDN && strlen(DeviceUDN) != (size_t)0) {if (strcasecmp(DeviceUDN, UDNstr)) {UpnpPrintf(UPNP_INFO, API, __FILE__, __LINE__,"DeviceUDN=%s and search UDN=%s DID NOT match\n",UDNstr, DeviceUDN);} else {UpnpPrintf(UPNP_INFO, API, __FILE__, __LINE__,"DeviceUDN=%s and search UDN=%s MATCH\n",UDNstr, DeviceUDN);SendReply(DestAddr, devType, 0, UDNstr, SInfo->DescURL, defaultExp, 0,SInfo->PowerState,SInfo->SleepPeriod,SInfo->RegistrationState);}   }/* clang-format on */ break;}case SSDP_DEVICETYPE: {/* clang-format off */if (!strncasecmp(DeviceType, devType, strlen(DeviceType) - (size_t)2)) {if (atoi(strrchr(DeviceType, ':') + 1) < atoi(&devType[strlen(devType) - (size_t)1])) {// /*请求的版本低于设备版本。设备版本必须使用较低的版本号和较低的描述URL进行回复*//*UpnpPrintf+SendReply*/UpnpPrintf(UPNP_INFO, API, __FILE__, __LINE__,"DeviceType=%s and search devType=%s MATCH\n",devType, DeviceType);SendReply(DestAddr, DeviceType, 0, UDNstr, SInfo->LowerDescURL,defaultExp, 1,SInfo->PowerState,SInfo->SleepPeriod,SInfo->RegistrationState);} else if (atoi(strrchr(DeviceType, ':') + 1)== atoi(&devType[strlen(devType) - (size_t)1])) {/*UpnpPrintf+SendReply*/UpnpPrintf(UPNP_INFO, API, __FILE__, __LINE__,"DeviceType=%s and search devType=%s MATCH\n",devType, DeviceType);SendReply(DestAddr, DeviceType, 0, UDNstr, SInfo->DescURL,defaultExp, 1,SInfo->PowerState,SInfo->SleepPeriod,SInfo->RegistrationState);} else {UpnpPrintf(UPNP_INFO, API, __FILE__, __LINE__,"DeviceType=%s and search devType=%s DID NOT MATCH\n",devType, DeviceType);}} else { UpnpPrintf(UPNP_INFO, API, __FILE__, __LINE__,"DeviceType=%s and search devType=%s DID NOT MATCH\n",devType, DeviceType);}/* clang-format on */break;}default:break;}}/* send service advertisements for services* corresponding to the same device */UpnpPrintf(UPNP_INFO,API,__FILE__,__LINE__,"Sending service Advertisement\n");/* Correct service traversal such that each device's* serviceList is directly traversed as a child of its* parent device. This ensures that the service's alive* message uses the UDN of the parent device. */tmpNode = ixmlNode_getFirstChild(tmpNode);while (tmpNode) {dbgStr = ixmlNode_getNodeName(tmpNode);if (!strncmp(dbgStr,SERVICELIST_STR,sizeof SERVICELIST_STR)) {break;}tmpNode = ixmlNode_getNextSibling(tmpNode);}ixmlNodeList_free(nodeList);if (!tmpNode) {nodeList = NULL;continue;}nodeList = ixmlElement_getElementsByTagName((IXML_Element *)tmpNode, "service");if (!nodeList) {UpnpPrintf(UPNP_INFO,API,__FILE__,__LINE__,"Service not found 3\n");continue;}for (j = 0lu;; j++) {tmpNode = ixmlNodeList_item(nodeList, j);if (!tmpNode) {break;}ixmlNodeList_free(tmpNodeList);tmpNodeList = ixmlElement_getElementsByTagName((IXML_Element *)tmpNode, "serviceType");if (!tmpNodeList) {UpnpPrintf(UPNP_CRITICAL,API,__FILE__,__LINE__,"ServiceType not found \n");continue;}tmpNode2 = ixmlNodeList_item(tmpNodeList, 0lu);if (!tmpNode2)continue;textNode = ixmlNode_getFirstChild(tmpNode2);if (!textNode)continue;/* servType is of format* Servicetype:ServiceVersion */tmpStr = ixmlNode_getNodeValue(textNode);if (!tmpStr)continue;strncpy(servType, tmpStr, sizeof(servType) - 1);UpnpPrintf(UPNP_INFO,API,__FILE__,__LINE__,"ServiceType = %s\n",servType);if (AdFlag) {if (AdFlag == 1) {ServiceAdvertisement(UDNstr,servType,SInfo->DescURL,Exp,SInfo->DeviceAf,SInfo->PowerState,SInfo->SleepPeriod,SInfo->RegistrationState);} else {/* AdFlag == -1 */ServiceShutdown(UDNstr,servType,SInfo->DescURL,Exp,SInfo->DeviceAf,SInfo->PowerState,SInfo->SleepPeriod,SInfo->RegistrationState);}} else {switch (SearchType) {case SSDP_ALL:ServiceReply(DestAddr,servType,UDNstr,SInfo->DescURL,defaultExp,SInfo->PowerState,SInfo->SleepPeriod,SInfo->RegistrationState);break;case SSDP_SERVICE:/* clang-format off */if (ServiceType) {if (!strncasecmp(ServiceType, servType, strlen(ServiceType) - (size_t)2)) {if (atoi(strrchr(ServiceType, ':') + 1) <atoi(&servType[strlen(servType) - (size_t)1])) {/* the requested version is lower than the service version* must reply with the lower version number and the lower* description URL */UpnpPrintf(UPNP_INFO, API, __FILE__, __LINE__,"ServiceType=%s and search servType=%s MATCH\n",ServiceType, servType);SendReply(DestAddr, ServiceType, 0, UDNstr, SInfo->LowerDescURL,defaultExp, 1,SInfo->PowerState,SInfo->SleepPeriod,SInfo->RegistrationState);} else if (atoi(strrchr (ServiceType, ':') + 1) ==atoi(&servType[strlen(servType) - (size_t)1])) {UpnpPrintf(UPNP_INFO, API, __FILE__, __LINE__,"ServiceType=%s and search servType=%s MATCH\n",ServiceType, servType);SendReply(DestAddr, ServiceType, 0, UDNstr, SInfo->DescURL,defaultExp, 1,SInfo->PowerState,SInfo->SleepPeriod,SInfo->RegistrationState);} else {UpnpPrintf(UPNP_INFO, API, __FILE__, __LINE__,"ServiceType=%s and search servType=%s DID NOT MATCH\n",ServiceType, servType);}} else {UpnpPrintf(UPNP_INFO, API, __FILE__, __LINE__,"ServiceType=%s and search servType=%s DID NOT MATCH\n",ServiceType, servType);}}/* clang-format on */break;default:break;}}}ixmlNodeList_free(tmpNodeList);tmpNodeList = NULL;ixmlNodeList_free(nodeList);nodeList = NULL;}}end_function:ixmlNodeList_free(tmpNodeList);ixmlNodeList_free(nodeList);UpnpPrintf(UPNP_ALL,API,__FILE__,__LINE__,"Exiting AdvertiseAndReply.\n");HandleUnlock();return retVal;
}

DeviceAdvertisement 根据输入参数创建设备广告请求

/*!* \brief 根据输入参数创建设备广告请求，并将其发送到多播通道。* \return 如果成功返回 UPNP_E_SUCCESS，否则返回适当的错误码。*/
int DeviceAdvertisement(char *DevType,/* [in] 设备的类型。 */int RootDev,/* [in] 标志，指示设备是否为根设备。 */char *Udn, /* [in] UDN（唯一设备名）。 */char *Location, /* [in] 位置 URL。 */int Duration,/* [in] 服务持续时间（秒）。 */int AddressFamily,/* [in] 设备地址族。 */int PowerState,/* [in] 根据 UPnP 低功耗标准定义的电源状态。 */int SleepPeriod,/* [in] 根据 UPnP 低功耗标准定义的睡眠周期。 */int RegistrationState /* [in] 根据 UPnP 低功耗标准定义的注册状态。 */);
{struct sockaddr_storage __ss;struct sockaddr_in *DestAddr4 = (struct sockaddr_in *)&__ss;struct sockaddr_in6 *DestAddr6 = (struct sockaddr_in6 *)&__ss;/* char Mil_Nt[LINE_SIZE] */char Mil_Usn[LINE_SIZE];char *msgs[3]; int ret_code = UPNP_E_OUTOF_MEMORY;	int rc = 0;UpnpPrintf(UPNP_INFO,SSDP,__FILE__,__LINE__,"In function DeviceAdvertisement\n");memset(&__ss, 0, sizeof(__ss));switch (AddressFamily) {case AF_INET:DestAddr4->sin_family = (sa_family_t)AF_INET;inet_pton(AF_INET, SSDP_IP, &DestAddr4->sin_addr);DestAddr4->sin_port = htons(SSDP_PORT);break;case AF_INET6:DestAddr6->sin6_family = (sa_family_t)AF_INET6;	inet_pton(AF_INET6,	 (isUrlV6UlaGua(Location)) ? SSDP_IPV6_SITELOCAL : SSDP_IPV6_LINKLOCAL, 	&DestAddr6->sin6_addr);DestAddr6->sin6_port = htons(SSDP_PORT); DestAddr6->sin6_scope_id = gIF_INDEX;break;default:UpnpPrintf(UPNP_CRITICAL,SSDP,__FILE__,__LINE__,"Invalid device address family.\n");}msgs[0] = NULL;	msgs[1] = NULL;	msgs[2] = NULL;/* If deviceis a root device , here we need to send 3 advertisement or reply */if (RootDev) {// 构建 USN 字符串：如果是根设备 (RootDev 为真)，则构建一个特殊的 USN（Unique Service Name），格式为 uuid::upnp:rootdevice。rc = snprintf(Mil_Usn, sizeof(Mil_Usn), "%s::upnp:rootdevice", Udn);if (rc < 0 || (unsigned int)rc >= sizeof(Mil_Usn))goto error_handler; //如果是根设备，那么会发送三条消息。CreateServicePacket(MSGTYPE_ADVERTISEMENT,"upnp:rootdevice",Mil_Usn,Location,Duration,&msgs[0],AddressFamily,PowerState,SleepPeriod,RegistrationState);}/* 创建消息  ： both root and sub-devices need to send these two messages 如果是子设备，那么会发送两条消息。*/CreateServicePacket(MSGTYPE_ADVERTISEMENT,Udn,Udn,Location,Duration,&msgs[1],AddressFamily,PowerState,SleepPeriod,RegistrationState);rc = snprintf(Mil_Usn, sizeof(Mil_Usn), "%s::%s", Udn, DevType);if (rc < 0 || (unsigned int)rc >= sizeof(Mil_Usn))goto error_handler;CreateServicePacket(MSGTYPE_ADVERTISEMENT,DevType,Mil_Usn,Location,Duration,&msgs[2],AddressFamily,PowerState,SleepPeriod,RegistrationState);/* check error */if ((RootDev && msgs[0] == NULL) || msgs[1] == NULL ||msgs[2] == NULL) {goto error_handler;}/* send packets */if (RootDev) { /* send 3 msg types */ret_code = NewRequestHandler((struct sockaddr *)&__ss, 3, &msgs[0]);} else { /* sub-device *//* send 2 msg types */ret_code = NewRequestHandler((struct sockaddr *)&__ss, 2, &msgs[1]);}
error_handler:/* free msgs */free(msgs[0]);free(msgs[1]);free(msgs[2]);return ret_code;
}

CreateServicePacket

/*!* \brief 创建一个 HTTP 请求包。根据输入参数，创建服务广告请求或服务关闭请求等。  静态函数，只能在此源文件内被调用。*/
static void CreateServicePacket(int msg_type,          /*!< [in] 消息类型 (回复、广告或关闭) */const char *nt,        /*!< [in] SSDP 类型 */char *usn,             /*!< [in] 唯一服务名称 (进入 HTTP 头部) */char *location,        /*!< [in] 位置 URL */int duration,          /*!< [in] 服务持续时间 (秒) */char **packet,         /*!< [out] 输出缓冲区填充 HTTP 语句 */int AddressFamily,     /*!< [in] HTTP 请求的地址族 */int PowerState,        /*!< [in] 根据 UPnP 低功耗标准定义的电源状态 */int SleepPeriod,       /*!< [in] 根据 UPnP 低功耗标准定义的睡眠周期 */int RegistrationState  /*!< [in] 根据 UPnP 低功耗标准定义的注册状态 */
) {// 主要调用 http_MakeMessage 函数创建
}

NewRequestHandler：HTTP 请求发送到一多播通道

  • 主要调用socket创建套接字，setsockopt配置套接字， sendto函数发送数据包。
/*!* \brief Works as a request handler which passes the HTTP request string* to multicast channel.** \return UPNP_E_SUCCESS if successful else appropriate error.*/
static int NewRequestHandler(/*! [in] Ip address, to send the reply. */struct sockaddr *DestAddr,/*! [in] Number of packet to be sent. */int NumPacket,/*! [in] . */char **RqPacket)
{char errorBuffer[ERROR_BUFFER_LEN];SOCKET ReplySock;socklen_t socklen = sizeof(struct sockaddr_storage);int Index;struct in_addr replyAddr;/* a/c to UPNP Spec */int ttl = 4;#ifdef UPNP_ENABLE_IPV6int hops = 1;#endifchar buf_ntop[INET6_ADDRSTRLEN];int ret = UPNP_E_SUCCESS;if (strlen(gIF_IPV4) > (size_t)0 &&!inet_pton(AF_INET, gIF_IPV4, &replyAddr)) {return UPNP_E_INVALID_PARAM;}ReplySock = socket((int)DestAddr->sa_family, SOCK_DGRAM, 0);if (ReplySock == INVALID_SOCKET) {strerror_r(errno, errorBuffer, ERROR_BUFFER_LEN);UpnpPrintf(UPNP_INFO,SSDP,__FILE__,__LINE__,"SSDP_LIB: New Request Handler:" "Error in socket(): %s\n",errorBuffer);return UPNP_E_OUTOF_SOCKET;}switch (DestAddr->sa_family) {case AF_INET:inet_ntop(AF_INET,&((struct sockaddr_in *)DestAddr)->sin_addr,buf_ntop,sizeof(buf_ntop));setsockopt(ReplySock,IPPROTO_IP,	IP_MULTICAST_IF,(char *)&replyAddr,	sizeof(replyAddr));setsockopt(ReplySock,IPPROTO_IP,IP_MULTICAST_TTL,(char *)&ttl,sizeof(int));socklen = sizeof(struct sockaddr_in);break;#ifdef UPNP_ENABLE_IPV6case AF_INET6:inet_ntop(AF_INET6,	&((struct sockaddr_in6 *)DestAddr)->sin6_addr,buf_ntop,sizeof(buf_ntop));setsockopt(ReplySock,IPPROTO_IPV6,IPV6_MULTICAST_IF,(char *)&gIF_INDEX,	sizeof(gIF_INDEX));setsockopt(ReplySock,IPPROTO_IPV6,IPV6_MULTICAST_HOPS,(char *)&hops,sizeof(hops));break;#endifdefault:UpnpPrintf(UPNP_CRITICAL,SSDP,__FILE__,__LINE__,"Invalid destination address specified.");ret = UPNP_E_NETWORK_ERROR;goto end_NewRequestHandler;}//  发送数据包for (Index = 0; Index < NumPacket; Index++) {ssize_t rc;UpnpPrintf(UPNP_INFO,SSDP,__FILE__,__LINE__,">>> SSDP SEND to %s >>>\n%s\n",buf_ntop,*(RqPacket + Index));rc = sendto(ReplySock,*(RqPacket + Index),strlen(*(RqPacket + Index)),0,DestAddr,socklen);if (rc == -1) {strerror_r(errno, errorBuffer, ERROR_BUFFER_LEN);UpnpPrintf(UPNP_INFO,SSDP,__FILE__,__LINE__,"SSDP_LIB: New Request Handler:""Error in socket(): %s\n",errorBuffer);ret = UPNP_E_SOCKET_WRITE;goto end_NewRequestHandler;}}end_NewRequestHandler:UpnpCloseSocket(ReplySock);return ret;
}

在这里插入图片描述

CG

  • https://datatracker.ietf.org/doc/html/draft-cai-ssdp-v1-03
  • Windows 10 : How to Start or Stop SSDP Discovery Service
  • https://github.com/zlargon/lssdp

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