UDP RTP packet frame loss

udp Packet loss ：
1. Sending packets continuously is too fast （ Each packet of data usleep(40)）;
2. Sending packet is too long （ Data is cut into 1400byte send out ）;
3. Too long processing time at the receiver leads to packet loss ： call recv Method the receiving end receives data after , It took some time to process the data , Call again after processing recv Method ,
Between these two calls , The bag sent may be lost . In this case, the receiving end can be modified , Store the received packet into a buffer , Then quickly return to continue recv.
4. The packet sent is large , Exceeding the recipient cache results in packet loss ： The bag exceeds mtu size several times , Several big udp The packet may exceed the recipient's buffer , Cause packet loss .
In this case, you can set socket Receive buffer . I have encountered this problem before , I set the receive buffer to 64K It's settled. .

Socket Buffer size modification and system settings ：（ Every Socket stay Linux Are mapped to a file , And with two buffers in the kernel （ Read buffer 、 Write buffer ） Related to . Or say , Every Socket Has two kernel buffers . Sometimes , We need to change the maximum kernel limit of the buffer , Make it meet our actual needs ）
cat /proc/sys/net/core/rmem_max 212992
rmem_max： One Socket The maximum value of the read buffer that can be set by the program , Unit byte ;
wmem_max： One Socket The maximum write buffer that can be set by the program , Unit byte ;
rmem_default： One Socket When is created , Default read buffer size , Unit byte ;
wmem_default： One Socket When is created , Default write buffer size , Unit byte ;

 Application level modification of buffer size 
 We can dynamically modify in the program （ adopt setsockopt system call ） Hold valid Socket Read / write buffer size of .

 Copy code 

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

int main(int argc, char **argv)
{
    
     if (argc != 2)
     {
    
         printf("Usage: %s $RCFBUFSIZE
", argv[0]);
         goto error;
     }

    int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
     if (sockfd < 0)
     {
    
         printf("create socket error=%d(%s)!!!
", errno, strerror(errno));
         goto error;
     }

    //  Check the system default socket Receive buffer size 
     int defRcvBufSize = -1;
     socklen_t optlen = sizeof(defRcvBufSize);
     if (getsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &defRcvBufSize, &optlen) < 0)
     {
    
         printf("getsockopt error=%d(%s)!!!
", errno, strerror(errno));
         goto error;
     }
     printf("OS default udp socket recv buff size is: %d
", defRcvBufSize);

    //  Set according to the execution parameters UDP SOCKET Receive buffer size 
     int rcvBufSize = atoi(argv[1]);
     if (rcvBufSize <= 0)
     {
    
         printf("rcvBufSize(%d) <= 0, error!!!
", rcvBufSize);
         goto error;
     }
     printf("you want to set udp socket recv buff size to %d
", rcvBufSize);
     optlen = sizeof(rcvBufSize);
     if (setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &rcvBufSize, optlen) < 0)
     {
    
         printf("setsockopt error=%d(%s)!!!
", errno, strerror(errno));
         goto error;
     }
     printf("set udp socket(%d) recv buff size to %d OK!!!
", sockfd, rcvBufSize);

    //  View the current UDP SOCKET Receive buffer size 
     int curRcvBufSize = -1;
     optlen = sizeof(curRcvBufSize);
     if (getsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &curRcvBufSize, &optlen) < 0)
     {
    
         printf("getsockopt error=%d(%s)!!!
", errno, strerror(errno));
         goto error;
     }
     printf("OS current udp socket(%d) recv buff size is: %d
", curRcvBufSize);

    close(sockfd);

    exit(0);

error:
     if (sockfd >= 0)
         close(sockfd);
     exit(1);
}