實戰Linux Bluetooth編程(六) L2CAP編程實例

例一：發送Signaling Packet：

Signaling Command是2個Bluetooth實體之間的L2CAP層命令傳輸。因此得Signaling Command使用CID 0x0001.

多個Command能夠在一個C-frame（control frame）中發送。

 

 若是要直接發送Signaling Command.須要創建SOCK_RAW類型的L2CAP鏈接Socket。這樣纔有機會本身填充Command Code，Identifier等。

 

如下是一個發送signaling Command以及接收Response的簡單例子：

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; //不要爲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); //建立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（）參數三是一個輸入輸出參數。輸入時，爲參數二的整體長度。輸出時，

//爲實際長度。
 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;  //如上圖所示，這一項爲此Command Identifier
 send_cmd->len   = htobs(size);
 send_cmd->code = L2CAP_ECHO_REQ;  //如上圖所示，此項爲Command code.這項定爲：

//Echo Request。對端會發送Response回來。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;
}

因此說，若是想要發送接收signaling Command。只須要創建l2cap RAW socket. 並按規則填充command id, command code等。就能夠接收發送了。

 

Command Code: 這個值放在l2cap.h中。

#define L2CAP_COMMAND_REJ 0x01
#define L2CAP_CONN_REQ  0x02
#define L2CAP_CONN_RSP  0x03
#define L2CAP_CONF_REQ  0x04
#define L2CAP_CONF_RSP  0x05
#define L2CAP_DISCONN_REQ 0x06
#define L2CAP_DISCONN_RSP 0x07
#define L2CAP_ECHO_REQ  0x08
#define L2CAP_ECHO_RSP  0x09
#define L2CAP_INFO_REQ  0x0a
#define L2CAP_INFO_RSP  0x0b

 

 

 

例二：任意PSM的L2CAP鏈接間數據的傳輸：

此例子中：Server，client實際上是使用網絡的概念定義的。

server用來監聽指定PSM的鏈接，並監聽數據。同時，利用poll來查看peer是否斷掉了。

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);  //發送數據，使用SOCK_SEQPACKET爲好
 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.每一個包的最大值
 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);  //獲得peer的信息

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

 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好像不準有無名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 網絡編程中,主動發起鏈接方，由於不關心地址具體是什麼，因此能夠做爲無名socket,也就是說能夠不bind. 但Bluetooth則不能夠，必定須要bind.

2. poll能夠查出鏈接斷連，但須要注意：斷開的revent值爲：11001B。也就是說：POLLIN | POLLERR |POLLHUP。

3. 被鏈接一方，必定要指定PSM。