CODEWITHSUNDEEP
c++udpwireshark
Skanda
Skanda

Reputation: 165

UDP header is filled more than what it is meant to be (42)

I am trying to send out data in UDP format (without handing any error - just opening the socket and send data). The code used is as below:

#include<iostream>
#include<arpa/inet.h>
#include<unistd.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<stdio.h>
#include<string.h>
#include<stdlib.h>

using namespace std;

int main()
{
    int sockfd;
    sockfd = socket(AF_INET,SOCK_DGRAM,0);
    struct sockaddr_in client;

    unsigned char* buffer = new unsigned char[1206]();
    for(auto i=0; i<1206; i++){
       buffer[i] = static_cast<unsigned char>(i);
    }

    client.sin_family = AF_INET;
    client.sin_port = htons(5005);
    client.sin_addr.s_addr = inet_addr("127.0.0.1");
    socklen_t m = sizeof(client);
    while(true){
         sendto(sockfd,buffer,1206 ,0,(struct sockaddr *)&client,m);
         cout<<"\nMessage sent...!! \n";  
     }  
}

However, this is not being recognized as UDP protocol. When tried to capture it using wireshark, I get following result. (1206 bytes of buffered data as expected but 44 bytes of header which should be 42). What is the problem with the code?

enter image description here

Upvotes: 0

Views: 338

Answers (1)

Naomi
Naomi

Reputation: 5486

Your code works just fine (tested on CentOS 7 with gcc 4.8.5). The capture method you are using is removing the Ethernet, IP and UDP layers, leaving you only with the payload.

Upvotes: 1

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