c-netapi2.html

Vxworks网络编程指南

</td>
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<div class="CellBody"><a name="89367"> </a></div>

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<div class="CellBody"><a name="89369"> </a>DVMRP routers. </div>

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<div class="CellBody"><a name="89371"> </a>224.0.0.5</div>

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<div class="CellBody"><a name="89373"> </a></div>

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<div class="CellBody"><a name="89375"> </a>OSPF routers. </div>

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<div class="CellBody"><a name="89377"> </a>224.0.0.6</div>

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<div class="CellBody"><a name="89379"> </a></div>

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<div class="CellBody"><a name="89381"> </a>OSPF designated routers. </div>

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<div class="CellBody"><a name="89383"> </a>224.0.0.9</div>

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<div class="CellBody"><a name="89385"> </a></div>

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<div class="CellBody"><a name="89387"> </a>All RIP routers. </div>

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<div class="CellBody"><a name="89389"> </a>224.0.0.255</div>

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<div class="CellBody"><a name="89391"> </a><b class="symbol_UC">INADDR_MAX_LOCAL_GROUP</b></div>

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<div class="CellBody"><a name="89393"> </a>Unassigned. </div>

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<div class="CellBody"><a name="89395"> </a>224.0.1.1</div>

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<div class="CellBody"><a name="89397"> </a></div>

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<div class="CellBody"><a name="89399"> </a>NTP (Network Time Protocol). </div>

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<dd><p class="Body"><a name="89401"> </a>The following code samples define two routines, <b class="routine"><i class="routine">mcastSend</i></b><b>(&nbsp;)</b> and <b class="routine"><i class="routine">mcastRcv</i></b><b>(&nbsp;)</b>. These routines demonstrate how to use UDP sockets to handle sending and receiving multicast traffic. </p>
<dd><p class="Body"><a name="89402"> </a><b class="routine"><i class="routine">mcastSend</i></b><b>(&nbsp;)</b> transmits a buffer to the specified multicast address. As input, this routine expects a multicast destination, a port number, a buffer pointer, and a buffer length. For example:</p>
<dl class="margin">

<dd><pre class="Code2"><b><a name="89403">status = mcastSend ("224.1.0.1", 7777, bufPtr, 100);</a></b></pre>
</dl>

<dd><p class="Body"><a name="89404"> </a><b class="routine"><i class="routine">mcastRcv</i></b><b>(&nbsp;)</b>receives any packet sent to a specified multicast address. As input, this routine expects the interface address from which the packet is coming, a multicast address, a port number, and the number of bytes to read from the packet. The returned value of the function is a pointer a buffer containing the read bytes. For example:</p>
<dl class="margin">

<dd><pre class="Code2"><b><a name="89405">buf = mcastRcv (ifAddress, "224.1.0.1", 7777, 100) ;</a></b></pre>
</dl>

</dl>

</dl>

<h4 class="EntityTitle"><a name="89406"><font face="Helvetica, sans-serif" size="-1" class="sans">Example 7-3:&nbsp;&nbsp;Datagram Sockets (UDP) and Multicasting </font></a></h4>
<dl class="margin">

<dl class="margin">

<dd><hr class="Line">
</dl>

<dl class="margin">

<dd><pre class="Code"><b><a name="89408">/* includes */ 
#include "vxWorks.h" 
#include "taskLib.h" 
#include "socket.h" 
#include "netinet/in.h" 
#include "stdio.h" 
#include "stdlib.h" 
#include "string.h" 
#include "sockLib.h" 
#include "inetLib.h" 
#include "ioLib.h" 
#include "routeLib.h" 
  
/* defines */ 
/* globals */ 
/* forward declarations */ 
 
 
STATUS mcastSend (char * mcastAddr, USHORT mcastPort, char * sendBuf, 
                  int sendLen);  
char * mcastRcv (char * ifAddr, char * mcastAddr, USHORT mcastPort,  
                 int numRead);  
 
/************************************************************************ 
* mcastSend - send a message to the multicast address 
* This function sends a message to the multicast address 
* The multicast group address to send, the port number, the pointer to the  
* send buffer and the send buffer length are given as input parameters. 
* RETURNS: OK if sucessful or ERROR 
*/ 
 
STATUS mcastSend 
    ( 
    char *      mcastAddr,      /* multicast address  */ 
    USHORT      mcastPort,      /* udp port number */ 
    char *      sendBuf,        /* send Buffer */ 
    int         sendLen         /* length of send buffer */ 
    ) 
    { 
    struct sockaddr_in  sin;  
    struct sockaddr_in  toAddr;  
    int                 toAddrLen; 
    int                 sockDesc; 
    char *              bufPtr; 
    int                 len; 
 
    /* create a send and recv socket */ 
 
    if ((sockDesc = socket (AF_INET, SOCK_DGRAM, 0)) &lt; 0 ) 
        { 
        printf (" cannot open send socket\n");  
        return (ERROR);  
        } 
 
    /* zero out the structures */ 
    bzero ((char *)&amp;sin, sizeof (sin)); 
    bzero ((char *)&amp;toAddr, sizeof (toAddr)); 
 
    sin.sa_len = (u_char) sizeof(sin);  
    sin.sin_family = AF_INET;  
    sin.sin_addr.s_addr = INADDR_ANY; 
    sin.sin_port = htons(0); 
 
    if (bind(sockDesc, (struct sockaddr *)&amp;sin, sizeof(sin)) != 0) 
        { 
        perror("bind"); 
        if (sockDesc) 
            close (sockDesc); 
        return (ERROR);  
        } 
 
    toAddrLen = sizeof(struct sockaddr_in); 
    toAddr.sa_len      = (u_char) toAddrLen; 
    toAddr.sin_family      = AF_INET; 
 
 
    /* initialize the address to the send */ 
    toAddr.sin_addr.s_addr = inet_addr (mcastAddr); 
 
    /* initialize the port to send */ 
    toAddr.sin_port        = htons(mcastPort); 
 
    bufPtr = sendBuf;           /* initialize the buffer pointer */ 
 
    /* send the buffer */ 
    while (sendLen &gt; 0) 
        { 
        if ((len = sendto (sockDesc, bufPtr, sendLen, 0,  
                           (struct sockaddr *)&amp;toAddr, toAddrLen)) &lt; 0 ) 
            { 
            printf("mcastSend sendto errno:0x%x\n", errno );  
            break; 
            } 
 
        sendLen -= len; 
        bufPtr += len; 
 
        taskDelay (1);          /* give  a taskDelay */ 
        } 
 
    if (sockDesc != ERROR) 
        close (sockDesc);  
 
    return (OK); 
    } 
 
/************************************************************************ 
 * mcastRcv - receive a message from a  multicast address 
 * This function receives a message from a  multicast address  
 * The interface address from which to receive the multicast packet, 
 * the multicast address to recv from, the port number and the number of  
 * bytes to read are given as input parameters to this routine. 
 * RETURNS: Pointer to the Buffer or NULL if error. 
 */ 
 
char * mcastRcv 
    ( 
    char *      ifAddr,         /* interface address to recv mcast packets */ 
    char *      mcastAddr,      /* multicast address  */ 
    USHORT      mcastPort,      /* udp port number to recv */ 
    int         numRead         /* number of bytes to read */ 
    ) 
    { 
    struct sockaddr_in  fromAddr;  
    struct sockaddr_in  sin;  
    int                 fromLen;  
    struct ip_mreq      ipMreq;  
    int                 recvLen; 
    int                 sockDesc; 
    char *              bufPtr;  
    int                 status  = OK; 
    char *              recvBuf = NULL; 
 
    if ((sockDesc = socket (AF_INET, SOCK_DGRAM, 0)) &lt; 0)  
        { 
        printf (" cannot open recv socket\n");  
        return (NULL); 
        } 
 
    bzero ((char *)&amp;sin, sizeof (sin)); 
    bzero ((char *) &amp;fromAddr, sizeof(fromAddr)); 
    fromLen = sizeof(fromAddr);  
 
    if ((recvBuf = calloc (numRead, sizeof (char))) == NULL) 
        { 
        printf (" calloc error, cannot allocate memory\n");  
        status = ERROR; 
        goto cleanUp; 
        } 
 
    sin.sa_len = (u_char) sizeof(sin);  
    sin.sin_family = AF_INET;  
    sin.sin_addr.s_addr = INADDR_ANY;  
 
    /* UDP port number to match for the received packets */ 
    sin.sin_port = htons (mcastPort); 
 
    /* bind a port number to the socket */ 
    if (bind(sockDesc, (struct sockaddr *)&amp;sin, sizeof(sin)) != 0) 
        { 
        perror("bind"); 
        status = ERROR; 
        goto cleanUp; 
        } 
     
    /* fill in the argument structure to join the multicast group */ 
    /* initialize the multicast address to join */ 
 
    ipMreq.imr_multiaddr.s_addr = inet_addr (mcastAddr); 
 
    /* unicast interface addr from which to receive the multicast packets */ 
    ipMreq.imr_interface.s_addr = inet_addr (ifAddr); 
     
    /* set the socket option to join the MULTICAST group */ 
    if (setsockopt (sockDesc, IPPROTO_IP, IP_ADD_MEMBERSHIP,  
                (char *)&amp;ipMreq,  
                sizeof (ipMreq)) &lt; 0) 
        {  
        printf ("setsockopt IP_ADD_MEMBERSHIP error:\n");  
        status = ERROR; 
        goto cleanUp; 
        } 
 
    /* get the data destined to the above multicast group */ 
    bufPtr = recvBuf; 
 
 
 
    while (numRead &gt; 0) 
      { 
      if ((recvLen = recvfrom (sockDesc, bufPtr, numRead, 0,  
                             (struct sockaddr *)&amp;fromAddr, &amp;fromLen)) &lt; 0) 
          { 
          perror("recvfrom");  
          status = ERROR; 
          break; 
          } 
       numRead -= recvLen;       /* decrement number of bytes to read */ 
      bufPtr  += recvLen;       /* increment the buffer pointer */ 
      } 
     
    /* set the socket option to leave the MULTICAST group */ 
    if (setsockopt (sockDesc, IPPROTO_IP, IP_DROP_MEMBERSHIP,  
                    (char *)&amp;ipMreq,  
                    sizeof (ipMreq)) &lt; 0)  
        printf ("setsockopt IP_DROP_MEMBERSHIP error:\n");  
 
    cleanUp: 
        { 
        if (sockDesc != ERROR) 
            close (sockDesc); 
         if ((status != OK) &amp;&amp; (recvBuf != NULL)) 
            { 
            free (recvBuf); 
            recvBuf = NULL; 
            } 
        } 
     return (recvBuf); 
    } 
</a></b></pre>
</dl>

</dl>


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