Client to Server Communication using a Message Queue
I'm implementing a program of communication by sending and receiving data between a server and a client:
I have a problem when writing data to a file and multiply it by 3.0. The program is only doing it for the first number stored in the file.
This is because when reading numbers from a file input.asc the program is read as a single message, and should read number by number and send to the server.
The file input.asc can have any number for example:
1.0
2.0
3.0
How to change this part of the code to read number by number to the message (msg.buffer)?
The part of the code to change itś brown.
Client:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <string.h>
#include <ctype.h>
#include <fcntl.h>
#define SERVER 1L
typedef struct {
long msg_to;
long msg_fm;
char buffer[BUFSIZ];
} MESSAGE;
int mid;
key_t key;
struct msqid_ds buf;
MESSAGE msg;
FILE *inFile;
int main(int argc, char** argv) {
//Aquiring Message Queue ID
key = ftok(".", 'z');
mid = msgget(key, 0);
//Display Message Queue and Client ID
printf("Message Queue ID: %d\n", mid);
printf("Client ID: %ld\n", (long)getpid());
//Opening input file, throw an error if invalid file
inFile = fopen("input.asc", "r");
if(inFile == NULL){
printf("Unable to open File = input.asc");
return 1;
}
//Copy input into msg.buffer, loops breaks when EOF is reached
int i = 0;
while(1){
msg.buffer[i] = fgetc(inFile);
if(msg.buffer[i]==EOF){
msg.buffer[i] = '\0';
break;
}
i++;
}
//Displaying message before conversion of server
printf("Message before conversion:\n");
printf("%s\n", msg.buffer);
//Getting Client PID and preparing message to message queue
long iD = (long)getpid();
msg.msg_to = SERVER;
msg.msg_fm = (long)getpid();
//Send message to Message Queue for Server, throws and error for invalid input
if(msgsnd(mid, &msg, sizeof(msg.buffer), 0)==-1){
perror("msgsnd");
exit(-1);
}
//Client waits for response from Server, throws an error if invalid input
if(msgrcv(mid, &msg, sizeof(msg), iD, 0)<0){
perror("msgrcv");
exit(-1);
}
//Display new converting message.
printf("Message after conversion\n");
printf("%s\n", msg.buffer);
//Removing message queue
msgctl(mid, IPC_RMID, (struct msqid_ds *) 0);
//Client exits
return (EXIT_SUCCESS);
}
Server:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <string.h>
#include <ctype.h>
#include <fcntl.h>
#define SERVER 1L
typedef struct {
long msg_to;
long msg_fm;
char buffer[BUFSIZ];
} MESSAGE;
int mid;
key_t key;
struct msqid_ds buf;
MESSAGE msg;
int inbin;
FILE *bin;
FILE *outasc;
int conta = 0;
int main(int argc, char** argv) {
//Creating a message queue
key = ftok(".", 'z');
if((mid = msgget(key, IPC_CREAT | 0660))<0){
printf("Error Creating Message Queue\n");
exit(-1);
}
//Display Message Queue and Server ID
printf("Message Queue ID: %d\n", mid);
printf("Server ID: %ld\n", (long)getpid());
//Receiving message from client, throws and error if input is invalid
if(msgrcv(mid, &msg, sizeof(msg.buffer), SERVER, 0)<0){
perror("msgrcv");
exit(-1);
}
//Aquiring Cliend PID to message return
long client = msg.msg_fm;
//Server displays received message
printf("SERVER receives:\n");
printf("%s\n", msg.buffer);
float aux=atof(msg.buffer);
printf("Conversion:%lf\n", aux);
//Creating the file input.bin
if((inbin = open("input.bin",O_WRONLY|O_TRUNC|O_CREAT,0600)) < 0)
{
perror("\nERROR NO input.bin!\n");
exit(1);
}
else
{
printf("\n File input.bin read\n");
printf("-------------------------\n\n");
int i=0;
while(msg.buffer[i] != '\0'){
write(inbin,&aux,sizeof(float));
i++;
conta++;
}
}
//Close the file input.bin
int closeinbin = close(inbin);
if(closeinbin < 0)
{
perror("\nERROR close the file input.bin\n");
exit(1);
}
float tab[conta];
//Open input.bin and saved the data
int readinbin = fread(&tab,sizeof(tab),1,(bin=fopen("input.bin","r")));
if(bin < 0 || readinbin < 0)
{
perror("\n ERROR open the file input.bin\n");
exit(1);
}
//Close the file input.bin
if(fclose(bin) < 0)
{
perror("\nERROR close the file input.bin!\n");
exit(1);
}
//Criar o output.asc//
if((outasc=fopen("output.asc","a")) < 0)
{
perror("ERROR open the file output.asc");
exit(1);
}
//Write in file output.asc//
int a;
for(a = 0; a < conta; a++)
{
char BUFFER[20];
tab[a] = 3.0*tab[a];
sprintf(BUFFER,"%f",tab[a]);
fputs(BUFFER,outasc);
fputs("\n",outasc);
printf("Wrote: %f \n",tab[a]);
}
if(fclose(outasc) < 0)
{
printf("ERROR close the file");
exit(1);
}
//prep return message
msg.msg_fm = SERVER;
msg.msg_to = client;
//send converting message back to client, throws and error if input is invalid
if(msgsnd(mid, (struct MESSAGE*)&msg, sizeof(msg.buffer), 0)==-1){
perror("msgsnd");
exit(-1);
}
//server exits
return (EXIT_SUCCESS);
}
