UDP receive queue and multiple initialization test

This period of time is based on udp The image is always stuck in the process of data playback , Find out recv Q Full of , But I don't know the specific reason , Here we go first udp Receiving test of .

One . Normal test  

1. send Each time the client sends 1k, Send frequency 50hz;

2. recv Every time you accept 1k, Acceptance frequency 5hz;
3. watch -n 1 netstat -anu Show recv The process corresponds to 8888 Port of recv Q stay 207000 To 162000 between , It won't get stuck .recv Q The upper limit of is 207000 about . By analyzing the results, we can find , When recv q After full ,recv Take it out of the queue 1k after , From the receiving and sending end 1k Enter the queue , It is recv Continue to get data from the queue , until recv Q drop to 162000 about , That is, the queue occupancy rate reaches 80% after , To accept send Data sent from the end .

Two . When recv End cnt==800 when , perform socket Reinitialize

 if(cnt == 800)

       {

          serfd=socket(AF_INET,SOCK_DGRAM,0);

           printf("serfd = %d\n",serfd);

          // ret=bind(serfd,(struct sockaddr *)&seraddr,sizeof(seraddr));

       }

1. socket initialization

  Whether implemented or not bind operation , The receiving end will get stuck , The receiving queue will be full . meanwhile /proc/pid/fd A new one will be added below socket file , Corresponding fd by 4. If you execute bind, Will return binding failure , Port occupied .

reason ： After the above if After the statement ,serfd Has become 4, The corresponding is a new socket file , in other words recv There will be a new receive queue at the end , Just no data is sent to this new queue .send The data sent by the end is still sent to serfd=3 In the corresponding queue , But no one reads the queue , cause recv Q Full of . The appearance is stuck , It's actually because serfd=4 There is no data in the corresponding queue .

    2. socket initialization , At the same time recvfrom Function serfd Switch to 3 This constant

In addition to the above modifications , If you put recvfrom Of serfd Change to constant 3, Although it is newly generated 4 Corresponding fd, But the data is still from 3 Get from the corresponding queue , And it won't get stuck , It's just 4 There is no data in the corresponding queue .

3、 ... and . When recv End cnt==800 when , perform socket Reinitialize

 if(cnt == 800)

 {

if(serfd>0) ret = close(serfd);

       printf("close serfd=%d\n",ret);

          serfd=socket(AF_INET,SOCK_DGRAM,0);

          sleep(1);

           printf("serfd = %d\n",serfd);

          ret=bind(serfd,(struct sockaddr *)&seraddr,sizeof(seraddr));

       }

reason ：

stay cnt by 800 when , The original fd Will close ,/proc/pid/fd/ The following file 3 It will also be deleted ; after , Re execution serfd=socket(AF_INET,SOCK_DGRAM,0); after , Will apply for available fd, And this time because 3 Number fd Has been released , So I reapplied fd still 3. It's just the corresponding inode The number has changed , from 2130436 Turned into 2132215. and 8888 The port corresponds to recv Q Medium 100 many k The data is cleared directly 0, Then start accumulating new data .

The test program

1. send End ：

#include <stdio.h>

#include <sys/socket.h>

#include <sys/types.h>

#include <string.h>

#include <unistd.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <iostream>

// establish UDP Realize the communication between server and client 

// establish socket Connect 

int main()

{

// establish socket Connect 

int clifd = 0;

int cnt = 0;

clifd = socket(AF_INET, SOCK_DGRAM, 0);

if (clifd < 0)

{

perror("socke failed");

return -1;

}

printf("socket success\n");

// Send a message to the server 

int tolen = 0;

int ret = 0;

char buf[1024] = {0};

while (1)

{



// std::cin.getline(buf,1023);

memset(buf, 0, 1024);

cnt++;

memcpy(buf, &cnt, sizeof(int));

struct sockaddr_in seraddr = {0};

seraddr.sin_family = AF_INET;

seraddr.sin_addr.s_addr = inet_addr("192.168.61.6");

seraddr.sin_port = htons(8888);

tolen = sizeof(seraddr);

ret = sendto(clifd, buf, strlen(buf), 0, (struct sockaddr *)&seraddr, tolen);

if (ret < 0)

{

perror("sendto failed");

close(clifd);

return -1;

}

printf("sendto success, %d\n", cnt);

// Receive messages sent from the server 

// ret=recvfrom(clifd,buf,sizeof(buf),0,NULL,NULL);

usleep(20000);

// if(ret<0)

// {

// perror("recvfrom failed");

// close(clifd);

// return -1;

// }

// printf("recvfrom success\n");

// printf("receive: %s\n",buf);

}

close(clifd);

return 0;

}

1. recv End

#include <stdio.h>

#include <sys/socket.h>

#include <sys/types.h>

#include <string.h>

#include <unistd.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <iostream>

// establish UDP Realize the communication between server and client 

int main()

{

// establish socket Connect 

int serfd = 0;

int cnt = 0;

serfd = socket(AF_INET, SOCK_DGRAM, 0);

printf("serfd = %d\n", serfd);

if (serfd < 0)

{

perror("socke failed");

return -1;

}

printf("socket success\n");

// binding IP Address and port information 

int ret = 0;

struct sockaddr_in seraddr = {0};

seraddr.sin_family = AF_INET;

seraddr.sin_addr.s_addr = inet_addr("192.168.61.6");

seraddr.sin_port = htons(8888);

ret = bind(serfd, (struct sockaddr *)&seraddr, sizeof(seraddr));

if (ret < 0)

{

perror("bind failed");

close(serfd);

return -1;

}

printf("bind success\n");

// Receive messages sent from clients 

unsigned int addrlen = 0;

char buf[1024] = {0};

struct sockaddr_in clientaddr = {0};

addrlen = sizeof(clientaddr);

while (1)

{

memset(buf, 0, 1024);



ret = recvfrom(serfd, buf, sizeof(buf), 0, (struct sockaddr *)&clientaddr, &addrlen);

if (ret < 0)

{

perror("recvfrom failed");

close(serfd);

return -1;

}

memcpy(&cnt, buf, sizeof(int));

printf("IP=%s,port=%u\n", inet_ntoa(clientaddr.sin_addr), ntohs(clientaddr.sin_port));

printf("recvfrom success\n");

printf("receive: %d\n", cnt);

if (cnt == 800)

{

if (serfd > 0)

ret = close(serfd);

printf("close serfd=%d\n", ret);

sleep(5);

serfd = socket(AF_INET, SOCK_DGRAM, 0);

sleep(1);

printf("serfd = %d\n", serfd);

ret = bind(serfd, (struct sockaddr *)&seraddr, sizeof(seraddr));

}

// Send a message to the client 

memset(buf, 0, sizeof(buf));

//gets(buf);

// std::cin.getline(buf,1023);

//cnt++;

//memcpy(buf,&cnt,sizeof(int));

// ret=sendto(serfd,buf,strlen(buf),0,(struct sockaddr *)&clientaddr,addrlen);

// if(ret<0)

// {

// printf("%ret = %d\n",ret);

// perror("sendto failed");

// close(serfd);

// return -1;

// }

// printf("sendto success\n");

usleep(200000);

}

close(serfd);

return 0;

}

compile ：

g++ recv.cpp -o recv

g++ send.cpp -o send

5、 ... and . Running order

1. preparation

start-up 6 A command window , Enter the above file directory ;

2. First in terminal#1 function recv Program , You can redirect it to other files ;

./recv > r3.txt

3. stay terminal#2 function send Program

./send

4. stay terminal#3 see rtxt Last 10 That's ok , Update every second , Mainly used to confirm cnt=800 About when ;

watch -n 1 tail -n10 r3.txt

 5. stay terminal#4 see recv Corresponding pid, And then into /proc/pid/fd see socket file , And update every second , see socket Whether the document has changed ;

6.  see udp Packet loss and socket Of the corresponding file inode Change or not ;

watch -n 1 "cat /proc/net/udp |grep 22B8" among 22B8 Is the port 8888 The hexadecimal representation of .

At present, packet loss 6121 individual ;2705799 At present 8888 Port correspondence socket Of documents inode Number . and /proc/pid/fd The following documents are consistent ;

 7.  see udp Reception queue of

watch -n 1 netstat -anu

You can see right now recv Q Keep running high .