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rsh_cli.c 9.79 KiB
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/un.h>
#include <fcntl.h>
#include "dshlib.h"
#include "rshlib.h"
/*
* exec_remote_cmd_loop(server_ip, port)
* server_ip: a string in ip address format, indicating the servers IP
* address. Note 127.0.0.1 is the default meaning the server
* is running on the same machine as the client
*
* port: The port the server will use. Note the constant
* RDSH_DEF_PORT which is 1234 in rshlib.h. If you are using
* tux you may need to change this to your own default, or even
* better use the command line override -c implemented in dsh_cli.c
* For example ./dsh -c 10.50.241.18:5678 where 5678 is the new port
* number and the server address is 10.50.241.18
*
* This function basically implements the network version of
* exec_local_cmd_loop() from the last assignemnt. It will:
*
* 1. Allocate buffers for sending and receiving data over the
* network
* 2. Create a network connection to the server, getting an active
* socket by calling the start_client(server_ip, port) function.
* 2. Go into an infinite while(1) loop prompting the user for
* input commands.
*
* a. Accept a command from the user via fgets()
* b. Send that command to the server using send() - it should
* be a null terminated string
* c. Go into a loop and receive client requests. Note each
* receive might not be a C string so you need to print it
* out using:
* printf("%.*s", (int)bytes_received, rsp_buff);
* this version of printf() uses the "%.*s" flag that indicates
* that the rsp_buff might be a null terminated string, or
* it might not be, if its not, print exactly bytes_received
* bytes.
* d. In the recv() loop described above. Each time you receive
* data from the server, see if the last byte received is the
* EOF character. This indicates the server is done and you can
* send another command by going to the top of the loop. The
* best way to do this is as follows assuming you are receiving
* data into a buffer called recv_buff, and you received
* recv_bytes in the call to recv:
*
* recv_bytes = recv(sock, recv_buff, recv_buff_sz, 0)
*
* if recv_bytes:
* <negative_number>: communication error
* 0: Didn't receive anything, likely server down
* > 0: Got some data. Check if the last byte is EOF
* is_eof = (recv_buff[recv_bytes-1] == RDSH_EOF_CHAR) ? 1 : 0;
* if is_eof is true, this is the last part of the transmission
* from the server and you can break out of the recv() loop.
*
* returns:
* OK: The client executed all of its commands and is exiting
* either by the `exit` command that terminates the client * or the `stop-server` command that terminates both the
* client and the server.
* ERR_MEMORY: If this function cannot allocate memory via
* malloc for the send and receive buffers
* ERR_RDSH_CLIENT: If the client cannot connect to the server.
* AKA the call to start_client() fails.
* ERR_RDSH_COMMUNICATION: If there is a communication error, AKA
* any failures from send() or recv().
*
* NOTE: Since there are several exit points and each exit point must
* call free() on the buffers allocated, close the socket, and
* return an appropriate error code. Its suggested you use the
* helper function client_cleanup() for these purposes. For example:
*
* return client_cleanup(cli_socket, request_buff, resp_buff, ERR_RDSH_COMMUNICATION);
* return client_cleanup(cli_socket, request_buff, resp_buff, OK);
*
* The above will return ERR_RDSH_COMMUNICATION and OK respectively to the main()
* function after cleaning things up. See the documentation for client_cleanup()
*
*/
int exec_remote_cmd_loop(char *address, int port)
{
char *cmd_buff;
char *rsp_buff;
int cli_socket;
ssize_t io_size;
int is_eof;
int rc = OK;
// Allocate buffers
cmd_buff = malloc(RDSH_COMM_BUFF_SZ);
rsp_buff = malloc(RDSH_COMM_BUFF_SZ);
if (cmd_buff == NULL || rsp_buff == NULL) {
return client_cleanup(-1, cmd_buff, rsp_buff, ERR_MEMORY);
}
// Connect to server
cli_socket = start_client(address, port);
if (cli_socket < 0){
perror("start client");
return client_cleanup(cli_socket, cmd_buff, rsp_buff, ERR_RDSH_CLIENT);
}
while (1)
{
printf(SH_PROMPT);
// get command input
if (fgets(cmd_buff, RDSH_COMM_BUFF_SZ, stdin) == NULL) {
break;
}
// remove trailing newline
cmd_buff[strcspn(cmd_buff, "\n")] = 0;
// send command to server (including null terminator)
if (send(cli_socket, cmd_buff, strlen(cmd_buff) + 1, 0) < 0) {
perror("send");
return client_cleanup(cli_socket, cmd_buff, rsp_buff, ERR_RDSH_COMMUNICATION);
}
// receive response from server
while ((io_size = recv(cli_socket, rsp_buff, RDSH_COMM_BUFF_SZ, 0)) > 0) {
// check if this is the last chunk
is_eof = (rsp_buff[io_size-1] == RDSH_EOF_CHAR) ? 1 : 0;
// print the received data
if (is_eof) {
printf("%.*s", (int)(io_size-1), rsp_buff); } else {
printf("%.*s", (int)io_size, rsp_buff);
}
// if EOF, receiving done
if (is_eof) {
break;
}
}
if (io_size < 0) {
perror("recv");
return client_cleanup(cli_socket, cmd_buff, rsp_buff, ERR_RDSH_COMMUNICATION);
}
if (io_size == 0) {
// server closed connection
return client_cleanup(cli_socket, cmd_buff, rsp_buff, ERR_RDSH_COMMUNICATION);
}
// exit command
if (strcmp(cmd_buff, EXIT_CMD) == 0) {
break;
}
}
return client_cleanup(cli_socket, cmd_buff, rsp_buff, OK);
}
/*
* start_client(server_ip, port)
* server_ip: a string in ip address format, indicating the servers IP
* address. Note 127.0.0.1 is the default meaning the server
* is running on the same machine as the client
*
* port: The port the server will use. Note the constant
* RDSH_DEF_PORT which is 1234 in rshlib.h. If you are using
* tux you may need to change this to your own default, or even
* better use the command line override -c implemented in dsh_cli.c
* For example ./dsh -c 10.50.241.18:5678 where 5678 is the new port
* number and the server address is 10.50.241.18
*
* This function basically runs the client by:
* 1. Creating the client socket via socket()
* 2. Calling connect()
* 3. Returning the client socket after connecting to the server
*
* returns:
* client_socket: The file descriptor fd of the client socket
* ERR_RDSH_CLIENT: If socket() or connect() fail
*
*/
int start_client(char *server_ip, int port){
struct sockaddr_in addr;
int cli_socket;
int ret;
// Create socket
cli_socket = socket(AF_INET, SOCK_STREAM, 0);
if (cli_socket == -1) {
perror("socket");
return ERR_RDSH_CLIENT;
}
// Set up address structure
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = inet_addr(server_ip);
addr.sin_port = htons(port);
// Connect to server
ret = connect(cli_socket, (struct sockaddr *)&addr, sizeof(addr));
if (ret == -1) {
perror("connect");
close(cli_socket);
return ERR_RDSH_CLIENT;
}
return cli_socket;
}
/*
* client_cleanup(int cli_socket, char *cmd_buff, char *rsp_buff, int rc)
* cli_socket: The client socket
* cmd_buff: The buffer that will hold commands to send to server
* rsp_buff: The buffer that will hld server responses
*
* This function does the following:
* 1. If cli_socket > 0 it calls close(cli_socket) to close the socket
* 2. It calls free() on cmd_buff and rsp_buff
* 3. It returns the value passed as rc
*
* Note this function is intended to be helper to manage exit conditions
* from the exec_remote_cmd_loop() function given there are several
* cleanup steps. We provide it to you fully implemented as a helper.
* You do not have to use it if you want to develop an alternative
* strategy for cleaning things up in your exec_remote_cmd_loop()
* implementation.
*
* returns:
* rc: This function just returns the value passed as the
* rc parameter back to the caller. This way the caller
* can just write return client_cleanup(...)
*
*/
int client_cleanup(int cli_socket, char *cmd_buff, char *rsp_buff, int rc){
//If a valid socket number close it.
if(cli_socket > 0){
close(cli_socket);
}
//Free up the buffers
free(cmd_buff);
free(rsp_buff);
//Echo the return value that was passed as a parameter
return rc;
}