I/O communication read and writing from client to server program - c

Question

So I am playing around with the idea of ports and client/server communication.
I have a server.c program that can open a port, open a listening descriptor, and upon receiving a connection, fork a child to handle communication with a connecting client. I have a client.c program that takes in 5 commandline arguments. Basically the first 3 arguments are practice strings to send to server and the 4th is hostname and the 5th is the port number.
So far connecting these two has worked fine, however, when client tries to write the 3 different strings (argv[1],argv[2], and argv[3]) to the server.c, server.c seems to only be able to read the first one then it seems to be stuck and not continue on with the additional reads even though client will finish writing all the strings to the communication file descriptor. I have been stuck for over 4 hours trying to figure out what should have been a simple practice program to better learn servers and clients. I don't wanna get anymore lost then I already am so I hope someone could anyone give me any advice on how to handle this issue or what I am doing wrong.
Client.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include "uici.h"
#include "func.h"
int main(int argc, char *argv[]){
int fd;
u_port_t portnum;
if(argc != 6){
fprintf(stderr, "Usage: %s string1 string2 string3 host port\n",argv[0]);
return -1;
}
portnum = (u_port_t)atoi(argv[5]);
if((fd = u_connect(portnum, argv[4])) == -1){
perror("Failled to establish connection");
return 1;
}
fprintf(stderr, "[%ld]:connection made to %s\n", (long)getpid(), argv[4]);
if((write(fd, argv[3], strlen(argv[3])+1)) == -1){
fprintf(stderr, "Failed to write %s to fd", argv[3]);
r_close(fd);
return 0;
}
if((write(fd, argv[1], strlen(argv[1])+1)) == -1){
fprintf(stderr, "Failed to write %s to fd", argv[1]);
r_close(fd);
return 0;
}
if((write(fd, argv[2], strlen(argv[2])+1)) == -1){
fprintf(stderr, "Failed to write %s to fd", argv[2]);
close(fd);
return 0;
}
fprintf(stderr, "Everything has been written\n");
return 0;
}
Server.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <limits.h>
#include <sys/types.h>
#include <sys/wait.h>
#include "func.h"
#include "uici.h"
int main(int argc, char *argv[])
{
u_port_t portnumber;
int listenfd;
int fd;
char client[MAX_CANON];
int bytes_copied;
pid_t child;
if (argc != 2) {
fprintf(stderr, "Usage: %s port\n", argv[0]);
return 1;
}
portnumber = (u_port_t) atoi(argv[1]);
if ((listenfd = u_open(portnumber)) < 0) {
perror("Listen endpoint creation failed");
return 1;
}
fprintf(stderr, "[%ld]: Waiting for the first connection on port %d\n",
(long)getpid(), (int)portnumber);
for ( ; ; ) {
if ((fd = u_accept(listenfd, client, MAX_CANON)) != -1) {
fprintf(stderr, "[%ld]: A connection has been received from %s\n",
(long) getpid(), client);
if ((child = fork()) == -1)
perror("Could not fork a child");
if (child == 0) { /* child code */
r_close(listenfd);
int MAXSZ = 1024;
char str3[MAXSZ];
char str1[MAXSZ];
char str2[MAXSZ];
int bytesread = 0;
fprintf(stderr, "Beginning the reads\n");
read(fd,str3, MAXSZ);
fprintf(stderr, "Finished 1st read\n");
read(fd,str1, MAXSZ);
fprintf(stderr, "Finished 2nd read\n");
read(fd,str2, MAXSZ);
fprintf(stderr, "str3: %s\n",str3);
fprintf(stderr, "str1 = %s\n",str1);
fprintf(stderr, "str2 = %s\n",str2);
close(fd);
return 0;
} else { /* parent code */
close(fd);
while (waitpid(-1, NULL, WNOHANG) > 0) ; /* clean up zombies */
}
}
else
perror("Accept failed");
}
}

Answer 1

First child forked closes the listener with r_close(listenfd);
Then when client send argv[1] no listener are available and, I think, u_accept(listenfd, client, MAX_CANON) return an error because of listenfd is not valid.

Answer 2

Note: There is no guarantee that read or write will read or write all the data from/to the file descriptor, and no guarantee that the data blocks the client is writing will be read in the same way on the server.
You have to make sure to check the bytes written and continue to write data to the fd until you have written them all. When reading, you have to have the client send some kind of header data describing the amount of data that is to be expected, or in your case, you could read 1 byte at a time and look for a '\0' character, indicating the end of a string.
Since MAXSZ is likely larger than the strings you are sending, the server could be reading all of the strings at once into the first buffer, then blocking on the subsequent read.