[源码级分析][android4.0]sdp Server的启动分析

SDP server是蓝牙启动过程中的一个非常重要部分。本文简单介绍一下这个函数的实现。

int start_sdp_server(uint16_t mtu, const char *did, uint32_t flags){//这里传入的flags是SDP_SERVER_COMPAT//所以compat值是有效的，master应该是0int compat = flags & SDP_SERVER_COMPAT;int master = flags & SDP_SERVER_MASTER;GIOChannel *io;info("Starting SDP server");//初始化server，详细见2.3.4.1if (init_server(mtu, master, compat) < 0) {error("Server initialization failed");return -1;}//did就是传入的device id，也就是main_opts.deviceid，他是根据DeviceID这个值来设置的，根据我们的main.conf，他的值就是android:generic:1.5if (did && strlen(did) > 0) {const char *ptr = did;uint16_t vid = 0x0000, pid = 0x0000, ver = 0x0000;//vid=android//pid=generic//version=1.5vid = (uint16_t) strtol(ptr, NULL, 16);ptr = strchr(ptr, ':');if (ptr) {pid = (uint16_t) strtol(ptr + 1, NULL, 16);ptr = strchr(ptr + 1, ':');if (ptr)ver = (uint16_t) strtol(ptr + 1, NULL, 16);//注册device id，仍然是一个service record的注册，不详细分析了，也会有UUIDS的property change哦register_device_id(vid, pid, ver);}}//对刚刚建的L2cap通道进行监听io = g_io_channel_unix_new(l2cap_sock);g_io_channel_set_close_on_unref(io, TRUE);//也就是accept了，处理函数是io_accept_eventl2cap_id = g_io_add_watch(io, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL,io_accept_event, &l2cap_sock);g_io_channel_unref(io);//若是compat，则对unix_sock进行监听，处理函数同样是io_accept_eventif (compat && unix_sock > fileno(stderr)) {io = g_io_channel_unix_new(unix_sock);g_io_channel_set_close_on_unref(io, TRUE);unix_id = g_io_add_watch(io,G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL,io_accept_event, &unix_sock);g_io_channel_unref(io);}return 0;}

2.3.4.1 init_server

这个从注释来看，就是sdp server的一些初始化，包括创建l2cap和unix socket用于discovery和registerclient来进行独立地访问。具体我们还是从代码的角度来分析：

static int init_server(uint16_t mtu, int master, int compat){struct l2cap_options opts;struct sockaddr_l2 l2addr;struct sockaddr_un unaddr;socklen_t optlen;/* Register the public browse group root *///注册public browse group root，不详细介绍，上面的service record创建中有详细介绍过register_public_browse_group();//注册一个sdp server的service record/* Register the SDP server's service record */register_server_service();//创建L2CAP的socket/* Create L2CAP socket */l2cap_sock = socket(PF_BLUETOOTH, SOCK_SEQPACKET, BTPROTO_L2CAP);if (l2cap_sock < 0) {error("opening L2CAP socket: %s", strerror(errno));return -1;}memset(&l2addr, 0, sizeof(l2addr));l2addr.l2_family = AF_BLUETOOTH;//addr 是anybacpy(&l2addr.l2_bdaddr, BDADDR_ANY);//psm是SDPl2addr.l2_psm = htobs(SDP_PSM);//就是把该l2cap和bdaddr_any绑定if (bind(l2cap_sock, (struct sockaddr *) &l2addr, sizeof(l2addr)) < 0) {error("binding L2CAP socket: %s", strerror(errno));return -1;}//要做master，其实我们默认配置可选的，所以，这里就不会走到了if (master) {int opt = L2CAP_LM_MASTER;if (setsockopt(l2cap_sock, SOL_L2CAP, L2CAP_LM, &opt, sizeof(opt)) < 0) {error("setsockopt: %s", strerror(errno));return -1;}}//设置mtu，默认传入的mtu是0，也就是使用kernel中的默认配置if (mtu > 0) {memset(&opts, 0, sizeof(opts));optlen = sizeof(opts);if (getsockopt(l2cap_sock, SOL_L2CAP, L2CAP_OPTIONS, &opts, &optlen) < 0) {error("getsockopt: %s", strerror(errno));return -1;}opts.omtu = mtu;opts.imtu = mtu;if (setsockopt(l2cap_sock, SOL_L2CAP, L2CAP_OPTIONS, &opts, sizeof(opts)) < 0) {error("setsockopt: %s", strerror(errno));return -1;}}//开始监听，最多5个，下面就可以accept了if (listen(l2cap_sock, 5) < 0) {error("listen: %s", strerror(errno));return -1;}//compat默认是1if (!compat) {unix_sock = -1;return 0;}//得到bluetooth的控制socket//这是和上层socket的一个通信，具体在上层用到的时候，我们再来分析        unix_sock = android_get_control_socket("bluetooth");        if (unix_sock < 0) {                error("Unable to get the control socket for 'bluetooth'");                return -1;        }//监听        if (listen(unix_sock, 5)) {                error("Listening on local socket failed: %s", strerror(errno));                return -1;        }        info("Got Unix socket fd '%d' from environment", unix_sock);}

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