linux下bluetooth编程（六）L2CAP层编程实例

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例一：发送Signaling Packet：

Signaling Command是2个Bluetooth实体之间的L2CAP层命令传输。所以得Signaling Command使用CID 0x0001.

多个Command可以在一个C-frame（control frame）中发送。

如果要直接发送Signaling Command.需要建立SOCK_RAW类型的L2CAP连接Socket。这样才有机会自己填充Command Code，Identifier等。

以下是一个发送signaling Command以及接收Response的简单例子：

int main(int argc, char** argv)
{
int l2_sck = 0; int iRel = 0; struct sockaddr_l2 local_l2_addr; struct sockaddr_l2 remote_l2_addr; char str[24] ={0}; int len = 0; int size = 50; char* send_buf; char* recv_buf; int i = 0; int id = 1; //不要为0 send_buf = malloc(L2CAP_CMD_HDR_SIZE + size); recv_buf = malloc(L2CAP_CMD_HDR_SIZE + size);

if(argc < 2) { printf("\n%s <bdaddr>\n", argv[0]); exit(0); }

// create l2cap raw socket l2_sck = socket(PF_BLUETOOTH, SOCK_RAW, BTPROTO_L2CAP); //创建L2CAP protocol的RAW Packet if(l2_sck < 0) { perror("\nsocket:"); return -1; }

//bind memset(&local_l2_addr, 0, sizeof(struct sockaddr_l2)); local_l2_addr.l2_family = PF_BLUETOOTH; bacpy(&local_l2_addr.l2_bdaddr , BDADDR_ANY);

iRel = bind(l2_sck, (struct sockaddr*) &local_l2_addr, sizeof(struct sockaddr_l2)); if(iRel < 0) { perror("\nbind()"); exit(0); }

//connect memset(&remote_l2_addr, 0 , sizeof(struct sockaddr_l2)); remote_l2_addr.l2_family = PF_BLUETOOTH; //printf("\nConnect to %s\n", argv[1]); str2ba(argv[1], &remote_l2_addr.l2_bdaddr);

iRel = connect(l2_sck, (struct sockaddr*)&remote_l2_addr, sizeof(struct sockaddr_l2)); if(iRel < 0) { perror("\nconnect()"); exit(0); }

//get local bdaddr len = sizeof(struct sockaddr_l2); memset(&local_l2_addr, 0, sizeof(struct sockaddr_l2));

//注意，getsockname（）参数三是一个输入输出参数。输入时，为参数二的总体长度。输出时，

//为实际长度。
iRel = getsockname(l2_sck, (struct sockaddr*) &local_l2_addr, &len); if(iRel < 0) { perror("\ngetsockname()"); exit(0); } ba2str(&(local_l2_addr.l2_bdaddr), str); //printf("\nLocal Socket bdaddr:[%s]\n", str); printf("l2ping: [%s] from [%s](data size %d) ...\n", argv[1], str, size);

for (i = 0; i < size; i++) send_buf[L2CAP_CMD_HDR_SIZE + i] = 'A';

l2cap_cmd_hdr *send_cmd = (l2cap_cmd_hdr *) send_buf; l2cap_cmd_hdr *recv_cmd = (l2cap_cmd_hdr *) recv_buf;

send_cmd->ident = id;//如上图所示，这一项为此Command Identifier send_cmd->len = htobs(size); send_cmd->code = L2CAP_ECHO_REQ;//如上图所示，此项为Command code.这项定为：

//Echo Request。对端会发送Response回来。code=L2CAP_ECHO_RSP

while(1) { send_cmd->ident = id; if(send(l2_sck, send_buf, size + L2CAP_CMD_HDR_SIZE, 0) <= 0) { perror("\nsend():"); } while(1) { if(recv(l2_sck, recv_buf, size + L2CAP_CMD_HDR_SIZE, 0) <= 0) { perror("\nrecv()"); } if (recv_cmd->ident != id) continue;

if( recv_cmd->code == L2CAP_ECHO_RSP) { //printf("\nReceive Response Packet.\n"); printf("%d bytes from [%s] id %d\n", recv_cmd->len, argv[1], recv_cmd->ident); break; } } sleep(1); id ++; }

close(l2_sck);

return 0; }

所以说，如果想要发送接收signaling Command。只需要建立l2cap RAW socket. 并按规则填充command id, command code等。就可以接收发送了。

Command Code: 这个值放在l2cap.h中。

#define L2CAP_COMMAND_REJ0x01 #define L2CAP_CONN_REQ0x02 #define L2CAP_CONN_RSP0x03 #define L2CAP_CONF_REQ0x04 #define L2CAP_CONF_RSP0x05 #define L2CAP_DISCONN_REQ0x06 #define L2CAP_DISCONN_RSP0x07 #define L2CAP_ECHO_REQ0x08 #define L2CAP_ECHO_RSP0x09 #define L2CAP_INFO_REQ0x0a #define L2CAP_INFO_RSP0x0b

例二：任意PSM的L2CAP连接间数据的传输：

此例子中：Server，client其实是使用网络的概念定义的。

server用来监听指定PSM的连接，并监听数据。同时，利用poll来查看peer是否断掉了。

Server：

#include <stdio.h>
#include <sys/types.h> #include <sys/socket.h> #include <stdlib.h> #include <poll.h>

#include <bluetooth/bluetooth.h>
#include <bluetooth/hci.h>
#include <bluetooth/hci_lib.h>
#include <bluetooth/l2cap.h>

void * Read_thread(void* pSK);

int main(int argc, char** argv)
{
int iRel = 0; int sk = 0; struct sockaddr_l2 local_addr; struct sockaddr_l2 remote_addr; int len; int nsk = 0; pthread_t nth = 0; struct l2cap_options opts; int optlen = 0; int slen = 0; char str[16] = {0};

if(argc < 2) { printf("\nUsage:%s psm\n", argv[0]); exit(0); }

// create l2cap socket sk = socket(PF_BLUETOOTH, SOCK_SEQPACKET, BTPROTO_L2CAP); //发送数据，使用SOCK_SEQPACKET为好 if(sk < 0) { perror("\nsocket():"); exit(0); }

//bind local_addr.l2_family = PF_BLUETOOTH; local_addr.l2_psm = htobs(atoi(argv[argc -1])); //last psm bacpy(&local_addr.l2_bdaddr, BDADDR_ANY); iRel = bind(sk, (struct sockaddr *)&local_addr, sizeof(struct sockaddr)); if(iRel < 0) { perror("\nbind()"); exit(0); }

//get opts

//in mtu 和 out mtu.每个包的最大值
memset(&opts, 0, sizeof(opts)); optlen = sizeof(opts); getsockopt(sk, SOL_L2CAP, L2CAP_OPTIONS, &opts, &optlen); printf("\nomtu:[%d]. imtu:[%d]. flush_to:[%d]. mode:[%d]\n", opts.omtu, opts.imtu, opts.flush_to, opts.mode);

//set opts. default value opts.omtu = 0; opts.imtu = 672; if (setsockopt(sk, SOL_L2CAP, L2CAP_OPTIONS, &opts, sizeof(opts)) < 0) { perror("\nsetsockopt():"); exit(0); }

//listen iRel = listen(sk, 10); if(iRel < 0) { perror("\nlisten()"); exit(0); }

len = sizeof(struct sockaddr_l2); while(1) { memset(&remote_addr, 0, sizeof(struct sockaddr_l2)); nsk = accept(sk, (struct sockaddr*)(&remote_addr), &len); if(nsk < 0) { perror("\naccept():"); continue; } ba2str(&(remote_addr.l2_bdaddr), str); printf("\npeer bdaddr:[%s].\n", str); //得到peer的信息

iRel = pthread_create(&nth, NULL, Read_thread, &nsk); if(iRel != 0) { perror("pthread_create():"); continue; } pthread_detach(nth); // 分离之 }

return 0; }

void * Read_thread(void* pSK)
{
//struct pollfd fds[10]; struct pollfd fds[100]; char buf[1024] = {0}; int iRel = 0; int exit_val = 0;

//fds[0].fd = *(int*)pSK; //fds[0].events = POLLIN | POLLHUP;

fds[0].fd = (int)(*(int*)pSK); fds[0].events = POLLIN | POLLHUP;

while(1) { if(poll(fds, 1, -1) < 0) { perror("\npoll():"); } if(fds[0].revents & POLLHUP) { //hang up printf("\n[%d] Hang up\n", *(int*)pSK); close(*(int*)pSK); pthread_exit(&exit_val);

break; }

if(fds[0].revents & POLLIN) { memset(buf, 0 , 1024); //read data iRel = recv(*(int*)pSK, buf, 572, 0); //printf("\nHandle[%d] Receive [%d] data:[%s]", *(int*)pSK, iRel, buf); } }

return 0; }

client:

#include <stdio.h>
#include <sys/types.h> #include <sys/socket.h> #include <unistd.h>

#include <bluetooth/bluetooth.h>
#include <bluetooth/hci.h>
#include <bluetooth/hci_lib.h>
#include <bluetooth/l2cap.h>

int main(int argc, char** argv)
{
int sk; int i = 0; char buf[24] = "Sam is Good Guy!"; struct sockaddr_l2 local_addr; struct sockaddr_l2 remote_addr; int iRel = 0;

if(argc < 3) { printf("\nUsage:%s <bdaddr> <PSM>\n", argv[0]); exit(0); }

sk = socket(PF_BLUETOOTH, SOCK_SEQPACKET, BTPROTO_L2CAP); if(sk < 0) { perror("\nsocket():"); exit(0); }

//bind. bluetooth好像不许有无名Socket local_addr.l2_family = PF_BLUETOOTH; bacpy(&local_addr.l2_bdaddr, BDADDR_ANY); iRel = bind(sk, (struct sockaddr *)&local_addr, sizeof(struct sockaddr)); if(iRel < 0) { perror("\nbind()"); exit(0); }

memset(&remote_addr, 0, sizeof(struct sockaddr_l2)); remote_addr.l2_family = PF_BLUETOOTH; str2ba(argv[1], &remote_addr.l2_bdaddr); remote_addr.l2_psm = htobs(atoi(argv[argc -1])); connect(sk, (struct sockaddr*)&remote_addr, sizeof(struct sockaddr_l2));

for(i = 0; i < 60; i++) { iRel = send(sk, buf, strlen(buf)+1, 0); printf("Send [%d] data\n", strlen(buf)+1); sleep(1); }

close(sk); return 0; }

注意：

1. 在Linux 网络编程中,主动发起连接方，因为不关心地址具体是什么，所以可以作为无名socket,也就是说可以不bind. 但Bluetooth则不可以，一定需要bind.

2. poll可以查出连接断连，但需要注意：断开的revent值为：11001B。也就是说：POLLIN | POLLERR |POLLHUP。

3. 被连接一方，一定要指定PSM。

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2011-09-17 15:47
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