Sendto: invalid argument error - c

Question

I'm creating a concurrent UDP socket for a university project. The client waits for a stdin command, then creates a new process and a new socket with the function child_job. The server receives the command from the client, creates a new process that initializes a new socket and then tries to send a string back to client. The problem is that the first sendto of the server create the error:
Invalid argument
I am not figuring out why. Can anyone help me please?
Code of the client:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/wait.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>
void child_job(int sockfd, struct sockaddr_in servaddr, char* buffer){
int n = sendto(sockfd, buffer, sizeof(buffer), 0, (struct sockaddr*)&servaddr, sizeof(servaddr));
if(n < 0){
perror("Error while sending roba to server\n");
exit(1);
}
printf("Connected to server\n");
char bufferaccio[128];
int length = sizeof(struct sockaddr);
int m = recvfrom(sockfd, bufferaccio, sizeof(bufferaccio), 0, (struct sockaddr*)&servaddr, (socklen_t *)&length);
if(m < 0){
perror("Error while receiving from server\n");
exit(1);
}
char stringa[128] = "I am a string from client";
m = sendto(sockfd, stringa, strlen(stringa), 0, (struct sockaddr *)&servaddr, sizeof(servaddr));
if(m < 0){
perror("Error while sending stringa to server\n");
exit(1);
}
exit(1);
}
int main(int argc, char** argv){
int sockfd;
struct sockaddr_in str;
if(argc < 3){
fprintf(stderr, "Usage: %s portno ip\n", argv[0]);
exit(1);
}
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if(sockfd < 0){
perror("Error while creating socket\n");
exit(1);
}
memset((void*)&str, 0, sizeof(str));
str.sin_family = AF_INET;
str.sin_port = htons(atoi(argv[1]));
if(inet_pton(AF_INET, argv[2], &str.sin_addr)< 0){
perror("Error while inet_pton\n");
exit(1);
}
pid_t pid;
char buffer[128];
printf("Write something to send\n");
scanf("%s", buffer);
pid = fork();
if(pid == 0){
printf("I am a children with pid %d\n", getpid());
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if(sockfd < 0){
perror("Error while creating socket in the child process\n");
exit(1);
}
child_job(sockfd, str, buffer);
}else if(pid < 0){
perror("Error while creating child process\n");
exit(1);
}
wait(NULL);
exit(1);
}
Code of the server:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <sys/types.h>
void initialize_newSocket(int* sock_fd, struct sockaddr_in *servaddr){
int sockfd;
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if(sockfd < 0){
perror("Error while creating new socket\n");
exit(1);
}
int ret = bind(sockfd, (struct sockaddr *)servaddr, sizeof(*servaddr));
if(ret < 0){
perror("Error while binding in son\n");
exit(1);
}
*sock_fd = sockfd;
}
void child_server_job(){
struct sockaddr_in addr;
int sockfd;
memset((void *)&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = INADDR_ANY;
addr.sin_port = htons(0);
initialize_newSocket(&sockfd, &addr);
char string[128] = "I am a string";
socklen_t fromlen = sizeof(addr);
int n = sendto(sockfd, string, strlen(string), 0, (struct sockaddr *)&addr, fromlen);
if(n < 0){
perror("Error while sending something\n");
exit(1);
}
int lenght = sizeof(struct sockaddr);
n = recvfrom(sockfd, string, strlen(string), 0, (struct sockaddr *)&addr, (socklen_t *)&lenght);
if(n < 0){
perror("Error while receveing data from client\n");
exit(1);
}
printf("I received this string %s\n", string);
exit(1);
}
int main(int argc, char** argv){
if(argc < 2){
fprintf(stderr, "Usage: %s portno\n", argv[0]);
exit(1);
}
int sockfd;
struct sockaddr_in addr;
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if(sockfd < 0){
perror("Error while creating socket\n");
exit(1);
}
addr.sin_family = AF_INET;
addr.sin_port = htons(atoi(argv[1]));
addr.sin_addr.s_addr = INADDR_ANY;
int retBind = bind(sockfd, (struct sockaddr*)&addr, sizeof(addr));
if(retBind < 0){
perror("Error while binding socket\n");
exit(1);
}
char bufferone[129];
int length = sizeof(struct sockaddr);
int n = recvfrom(sockfd, bufferone, sizeof(bufferone), 0, (struct sockaddr*)&addr, (socklen_t *)&length);
if(n < 0){
perror("Error while receiving roba from client\n");
exit(1);
}
printf("Printing: %s\n", bufferone);
pid_t pid = fork();
if(pid == 0){
printf("I am the child with pid %d\n", getpid());
child_server_job(sockfd, addr);
exit(1);
}else if(pid < 0){
perror("Error while forking new process\n");
exit(1);
}
wait(NULL);
exit(1);
}
Client output:
Write something to send
string
I am a children with pid 5756
Connected to server
Server output:
Printing: string
I am the child with pid 5757
Now it's my turn to send something
Error while sending something
: Invalid argument

Answer 1

The function "child_server_job" does not use passed parameters!
change the child_server_job to give parameter and use the passed parameters.
Edit
void child_server_job(){
struct sockaddr_in addr;
int sockfd;
memset((void *)&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = INADDR_ANY;
addr.sin_port = htons(0);
initialize_newSocket(&sockfd, &addr);
To:
void child_server_job(int* sock_fd, struct sockaddr_in *servaddr){
struct sockaddr_in addr = *servaddr;
int sockfd = *sock_fd;
/*memset((void *)&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = INADDR_ANY;
addr.sin_port = htons(0);
initialize_newSocket(&sockfd, &addr); */
AND
child_server_job(sockfd, addr);
To:
child_server_job(&sockfd, &addr);