UDP Client Server invalid argument - c

Question

I have a server that is supposed to send information to a client after receiving a message from the client (echo server). Below is the code that is producing an errno 22 which i looked up as "invalid argument". I am trying to understand which argument is invalid because my client sends a message with the same arguments
#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
//#include <sys/time.h>
int main(int argc, char *argv[]) {
// port to start the server on
int SERVER_PORT = 8877;
struct timeval server_start, client_start;
// socket address used for the server
struct sockaddr_in server_address;
memset(&server_address, 0, sizeof(server_address));
server_address.sin_family = AF_INET;
// htons: host to network short: transforms a value in host byte
// ordering format to a short value in network byte ordering format
server_address.sin_port = htons(SERVER_PORT);
// htons: host to network long: same as htons but to long
server_address.sin_addr.s_addr = htonl(INADDR_ANY);
// create a UDP socket, creation returns -1 on failure
int sock;
if ((sock = socket(PF_INET, SOCK_DGRAM, 0)) < 0) {
printf("could not create socket\n");
return 1;
}
// bind it to listen to the incoming connections on the created server
// address, will return -1 on error
if ((bind(sock, (struct sockaddr *)&server_address,
sizeof(server_address))) < 0) {
printf("could not bind socket\n");
return 1;
}
// socket address used to store client address
struct sockaddr_in client_address;
int client_address_len = 0;
// run indefinitely
while (true) {
char buffer[500];
printf("problem here \n");
int len=0;
// read content into buffer from an incoming client
if (len = recvfrom(sock, &client_start, sizeof(client_start), 0,(struct sockaddr *)&client_address,&client_address_len)<0){
printf("failed: %d\n", errno);
return 1;
}
// inet_ntoa prints user friendly representation of the
// ip address
//buffer[len] = '\0';
gettimeofday(&server_start);
int send = 0;
// send same content back to the client ("echo")
if(send = sendto(sock, &server_start, sizeof(server_start),0,(struct sockaddr *)&client_address,
&client_address_len)<0){
printf("failed: %d\n", errno);
return 1;
};
}
return 0;
}

Answer 1

I am trying to understand which argument is invalid
No argument is invalid. You got a false positive on your error testing.
if (len = recvfrom(sock, &client_start, sizeof(client_start), 0,(struct sockaddr *)&client_address,&client_address_len)<0){
if(send = sendto(sock, &server_start, sizeof(server_start),0,(struct sockaddr *)&client_address,
&client_address_len)<0){
Usual problem. Operator precedence. Try this:
if ((len = recvfrom(sock, &client_start, sizeof(client_start), 0,(struct sockaddr *)&client_address,&client_address_len))<0){
if((send = sendto(sock, &server_start, sizeof(server_start),0,(struct sockaddr *)&client_address,
&client_address_len))<0){