Server and client data send() and recv() issue - c

Question

I have been trying to write a client and server program using C socket programming that does 2 tasks
On prompted from server -> OS command is executed in client machine
Output is stored in a file which is sent back to server. Where server reads it and displays the data plus writes the data in a file on server side.
Issue
When client sends file to the server, server does not display whole data and looks like recv() keeps waiting on socket.
Need some help
Here's the code
server code
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#define SIZE 1024
void write_file(char *filename,int sockfd){
int n;
FILE *fp ;
char buffer[SIZE] ;
fp = fopen(filename, "w");
while (1) {
n = recv(sockfd, buffer, SIZE, 0);
if (n <= 0){
break;
return;
}
printf("%s", buffer) ;
fprintf(fp, "%s", buffer);
bzero(buffer, SIZE);
}
fclose(fp) ;
return;
}
int main(int argc, char *argv[]){
int portno = 7416;
int e,n,n1;
char *cmd ;
int sockfd;
struct sockaddr_in server_addr;
struct hostent *server;
char *fle = "/tmp/reposvr.";
FILE *fp;
char *num ;
if (argc < 3) {
fprintf(stderr,"usage %s hostname command \n", argv[0]);
exit(0);
}
cmd=argv[2] ;
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if(sockfd < 0) {
perror("[-]Error in socket");
exit(1);
}
printf("[+]Server socket created successfully.\n");
server = gethostbyname(argv[1]);
if (server == NULL) {
fprintf(stderr,"ERROR, no such host\n");
exit(0);
}
//server_addr.sin_family = AF_INET;
//server_addr.sin_port = port;
//server_addr.sin_addr.s_addr = inet_addr(ip);
bzero((char *) &server_addr, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(portno);
server_addr.sin_addr = *((struct in_addr *)server->h_addr);
memset(server_addr.sin_zero, '\0', sizeof server_addr.sin_zero);
e = connect(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr));
if(e == -1) {
perror("[-]Error in socket");
exit(1);
}
printf("[+]Connected to Server.\n");
n = write(sockfd, cmd , strlen(cmd));
if (n < 0)
error("ERROR writing to socket");
char *filename=NULL;
filename = (char*)malloc( 50 * sizeof(char) ) ;
strcpy(filename,fle );
n1=rand();
if (asprintf(&num, "%d", n1) == -1) {
perror("asprintf");
} else {
strcat(filename, num);
printf("%s\n", filename);
free(num);
}
printf("%s\n",filename) ;
write_file(filename,sockfd) ;
printf("[+]File data sent successfully.\n");
printf("[+]Closing the connection.\n");
close(sockfd);
return 0;
}
Client code
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#define SIZE 1024
void send_file(FILE *fp, int sockfd){
int n;
char data[SIZE] = {0};
while(fgets(data, SIZE, fp) != NULL) {
if (send(sockfd, data, sizeof(data), 0) == -1) {
perror("[-]Error in sending file.");
exit(1);
}
bzero(data, SIZE);
}
}
int main(){
int port = 7416;
int e,n1, n ;
FILE *fp ;
char filename[50] = "/tmp/gateway." ;
char command[50];
char *num;
FILE *pf;
char data[SIZE];
int sockfd, new_sock;
struct sockaddr_in server_addr, new_addr;
socklen_t addr_size;
char buffer[SIZE];
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if(sockfd < 0) {
perror("[-]Error in socket");
exit(1);
}
printf("[+]Server socket created successfully.\n");
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(port);
server_addr.sin_addr.s_addr = INADDR_ANY;
e = bind(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr));
if(e < 0) {
perror("[-]Error in bind");
exit(1);
}
printf("[+]Binding successfull.\n");
if(listen(sockfd, 10) == 0){
printf("[+]Listening....\n");
}else{
perror("[-]Error in listening");
exit(1);
}
addr_size = sizeof(new_addr);
while ( new_sock = accept(sockfd, (struct sockaddr*)&new_addr, &addr_size) )
{
printf("server: got connection from %s port %d\n",
inet_ntoa(new_addr.sin_addr), ntohs(new_addr.sin_port));
n = read(new_sock,buffer,1024);
if (n < 0) error("ERROR reading from socket");
strcpy(command, buffer) ;
printf("%s",command) ;
pf = popen(command,"r");
bzero(data,1024);
n1=rand();
if (asprintf(&num, "%d", n1) == -1) {
perror("asprintf");
} else {
strcat(filename, num);
printf("%s\n", filename);
free(num);
}
printf("%s",filename) ;
fp=fopen(filename,"w" );
while (fgets(data, 2048, pf) != NULL) {
printf("%s", data);
fprintf(fp, "%s",data) ;
}
fclose(fp) ;
fp = fopen(filename, "r");
if (fp == NULL) {
perror("[-]Error in reading file.");
exit(1);
}
send_file(fp, new_sock);
printf("[+]Data written in the file successfully.\n");
}
return 0;
}
Execution output
Edit
Based on the suggestions in this forum, I increased SIZE to 2048 and found that now it returns less rows and hangs after 4-5 rows itself. This is weird. I am sure it's not because of SIZE.
If you see, in client side, we are able to successfully write all in a file. Second part of the program is to read from file and send it to server. Here I am iterating through whole file and sending the data to server. The data send loop is working nicely as I have printf in same loop and we can see all data getting printed.
Looking at server side, here also we are looping till number of bytes read are < 1. Theoretically, this should work. I am sure there's some tiny silly thing that I am missing. Just not able to put my finger on it. Really need some insights in here.
Edit 2
Already tried SIZE , MSG_PEEK as you can see in comments. Any more suggestions ?