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rsh_server.c
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Ziheng Chen authoredZiheng Chen authored
rsh_server.c 24.99 KiB
#include <sys/socket.h>
#include <sys/wait.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 <signal.h>
#include <pthread.h>
//INCLUDES for extra credit
//#include <signal.h>
//#include <pthread.h>
//-------------------------
#include "dshlib.h"
#include "rshlib.h"
typedef struct {
int cli_socket;
} client_thread_args_t;
// Function to handle client in a separate thread
void *client_handler(void *args) {
client_thread_args_t *client_args = (client_thread_args_t *)args;
exec_client_requests(client_args->cli_socket);
close(client_args->cli_socket);
free(client_args);
pthread_exit(NULL);
}
/*
* start_server(ifaces, port, is_threaded)
* ifaces: a string in ip address format, indicating the interface
* where the server will bind. In almost all cases it will
* be the default "0.0.0.0" which binds to all interfaces.
* note the constant RDSH_DEF_SVR_INTFACE in rshlib.h
*
* 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 -s implemented in dsh_cli.c
* For example ./dsh -s 0.0.0.0:5678 where 5678 is the new port
*
* is_threded: Used for extra credit to indicate the server should implement
* per thread connections for clients
*
* This function basically runs the server by:
* 1. Booting up the server
* 2. Processing client requests until the client requests the
* server to stop by running the `stop-server` command
* 3. Stopping the server.
*
* This function is fully implemented for you and should not require
* any changes for basic functionality.
*
* IF YOU IMPLEMENT THE MULTI-THREADED SERVER FOR EXTRA CREDIT YOU NEED
* TO DO SOMETHING WITH THE is_threaded ARGUMENT HOWEVER.
*/
int start_server(char *ifaces, int port, int is_threaded){
int svr_socket;
int rc;
//(void)is_threaded; // Suppress unused parameter warning
//
//TODO: If you are implementing the extra credit, please add logic
// to keep track of is_threaded to handle this feature
//
svr_socket = boot_server(ifaces, port);
if (svr_socket < 0){
int err_code = svr_socket; //server socket will carry error code
return err_code;
}
printf("Server started in %s mode.\n", is_threaded ? "Multi-Threaded" : "Single-Threaded");
rc = process_cli_requests(svr_socket, is_threaded);
stop_server(svr_socket);
return rc;
}
/*
* stop_server(svr_socket)
* svr_socket: The socket that was created in the boot_server()
* function.
*
* This function simply returns the value of close() when closing
* the socket.
*/
int stop_server(int svr_socket){
return close(svr_socket);
}
/*
* boot_server(ifaces, port)
* ifaces & port: see start_server for description. They are passed
* as is to this function.
*
* This function "boots" the rsh server. It is responsible for all
* socket operations prior to accepting client connections. Specifically:
*
* 1. Create the server socket using the socket() function.
* 2. Calling bind to "bind" the server to the interface and port
* 3. Calling listen to get the server ready to listen for connections.
*
* after creating the socket and prior to calling bind you might want to
* include the following code:
*
* int enable=1;
* setsockopt(svr_socket, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int));
*
* when doing development you often run into issues where you hold onto
* the port and then need to wait for linux to detect this issue and free
* the port up. The code above tells linux to force allowing this process
* to use the specified port making your life a lot easier.
*
* Returns:
*
* server_socket: Sockets are just file descriptors, if this function is
* successful, it returns the server socket descriptor,
* which is just an integer.
*
* ERR_RDSH_COMMUNICATION: This error code is returned if the socket(),
* bind(), or listen() call fails.
*
*/
int boot_server(char *ifaces, int port) {
int svr_socket;
struct sockaddr_in server_addr;
int enable = 1;
// Step 1: Create a socket
svr_socket = socket(AF_INET, SOCK_STREAM, 0);
if (svr_socket < 0) {
perror("Error creating server socket");
fprintf(stderr, CMD_ERR_RDSH_COMM);
return ERR_RDSH_COMMUNICATION;
}
// Step 2: Set socket options to allow address reuse
if (setsockopt(svr_socket, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int)) < 0) {
perror("Error setting socket options");
fprintf(stderr, CMD_ERR_RDSH_COMM);
close(svr_socket);
return ERR_RDSH_COMMUNICATION;
}
// Step 3: Prepare server address structure
memset(&server_addr, 0, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(port); // Convert port to network byte order
// Convert and assign the interface IP
if (inet_pton(AF_INET, ifaces, &server_addr.sin_addr) <= 0) {
perror("Invalid server IP address");
fprintf(stderr, CMD_ERR_RDSH_COMM);
close(svr_socket);
return ERR_RDSH_COMMUNICATION;
}
// Step 4: Bind the socket
if (bind(svr_socket, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
perror("Error binding server socket");
fprintf(stderr, CMD_ERR_RDSH_COMM);
close(svr_socket);
return ERR_RDSH_COMMUNICATION;
}
// Step 5: Put the socket in listening mode
if (listen(svr_socket, SOMAXCONN) < 0) {
perror("Error setting server to listen mode");
fprintf(stderr, CMD_ERR_RDSH_COMM);
close(svr_socket);
return ERR_RDSH_COMMUNICATION;
}
printf("Server listening on %s:%d\n", ifaces, port);
return svr_socket;
//return WARN_RDSH_NOT_IMPL;
}
/*
* process_cli_requests(svr_socket)
* svr_socket: The server socket that was obtained from boot_server()
*
* This function handles managing client connections. It does this using
* the following logic
*
* 1. Starts a while(1) loop:
*
* a. Calls accept() to wait for a client connection. Recall that
* the accept() function returns another socket specifically
* bound to a client connection.
* b. Calls exec_client_requests() to handle executing commands
* sent by the client. It will use the socket returned from
* accept().
* c. Loops back to the top (step 2) to accept connecting another
* client.
* * note that the exec_client_requests() return code should be
* negative if the client requested the server to stop by sending
* the `stop-server` command. If this is the case step 2b breaks
* out of the while(1) loop.
*
* 2. After we exit the loop, we need to cleanup. Dont forget to
* free the buffer you allocated in step #1. Then call stop_server()
* to close the server socket.
*
* Returns:
*
* OK_EXIT: When the client sends the `stop-server` command this function
* should return OK_EXIT.
*
* ERR_RDSH_COMMUNICATION: This error code terminates the loop and is
* returned from this function in the case of the accept()
* function failing.
*
* OTHERS: See exec_client_requests() for return codes. Note that positive
* values will keep the loop running to accept additional client
* connections, and negative values terminate the server.
*
*/
/*
int process_cli_requests(int svr_socket) {
int cli_socket;
int rc;
while (1) {
// Step 1: Accept an incoming client connection
cli_socket = accept(svr_socket, NULL, NULL);
if (cli_socket < 0) {
perror("Error accepting client connection");
fprintf(stderr, CMD_ERR_RDSH_COMM);
return ERR_RDSH_COMMUNICATION;
}
printf("Client connected\n");
// Step 2: Handle client requests
rc = exec_client_requests(cli_socket);
// Step 3: Close client socket after handling requests
close(cli_socket);
printf(RCMD_MSG_CLIENT_EXITED);
// Step 4: If client requested server to stop, break loop
if (rc == OK_EXIT) {
printf(RCMD_MSG_SVR_STOP_REQ);
break;
}
}
return OK_EXIT;
//return WARN_RDSH_NOT_IMPL;
}
*/
int process_cli_requests(int svr_socket, int is_threaded) {
int cli_socket;
int rc;
while (1) {
// Step 1: Accept a client connection
cli_socket = accept(svr_socket, NULL, NULL);
if (cli_socket < 0) { perror("Error accepting client connection");
fprintf(stderr, CMD_ERR_RDSH_COMM);
return ERR_RDSH_COMMUNICATION;
}
//printf("Client connected\n");
printf("Client connected (socket %d)\n", cli_socket);
fflush(stdout);
// Multi-threaded mode: Create a new thread for each client
if (is_threaded) {
pthread_t client_thread;
client_thread_args_t *args = malloc(sizeof(client_thread_args_t));
if (!args) {
perror("Memory allocation failed for client thread");
close(cli_socket);
continue;
}
args->cli_socket = cli_socket;
if (pthread_create(&client_thread, NULL, client_handler, (void *)args) != 0) {
perror("Failed to create client thread");
free(args);
close(cli_socket);
continue;
}
// Detach thread so it cleans up after itself
pthread_detach(client_thread);
} else {
// Single-threaded mode: Handle client in main thread
rc = exec_client_requests(cli_socket);
close(cli_socket);
printf(RCMD_MSG_CLIENT_EXITED);
if (rc == OK_EXIT) {
printf(RCMD_MSG_SVR_STOP_REQ);
break;
}
}
}
return OK_EXIT;
}
/*
* exec_client_requests(cli_socket)
* cli_socket: The server-side socket that is connected to the client
*
* This function handles accepting remote client commands. The function will
* loop and continue to accept and execute client commands. There are 2 ways
* that this ongoing loop accepting client commands ends:
*
* 1. When the client executes the `exit` command, this function returns
* to process_cli_requests() so that we can accept another client
* connection.
* 2. When the client executes the `stop-server` command this function
* returns to process_cli_requests() with a return code of OK_EXIT
* indicating that the server should stop.
*
* Note that this function largely follows the implementation of the
* exec_local_cmd_loop() function that you implemented in the last
* shell program deliverable. The main difference is that the command will
* arrive over the recv() socket call rather than reading a string from the
* keyboard.
*
* This function also must send the EOF character after a command is
* successfully executed to let the client know that the output from the * command it sent is finished. Use the send_message_eof() to accomplish
* this.
*
* Of final note, this function must allocate a buffer for storage to
* store the data received by the client. For example:
* io_buff = malloc(RDSH_COMM_BUFF_SZ);
* And since it is allocating storage, it must also properly clean it up
* prior to exiting.
*
* Returns:
*
* OK: The client sent the `exit` command. Get ready to connect
* another client.
* OK_EXIT: The client sent `stop-server` command to terminate the server
*
* ERR_RDSH_COMMUNICATION: A catch all for any socket() related send
* or receive errors.
*/
int exec_client_requests(int cli_socket) {
char *io_buff;
ssize_t recv_size;
int rc;
// Step 1: Allocate buffer for receiving client data
io_buff = (char *)malloc(RDSH_COMM_BUFF_SZ);
if (!io_buff) {
fprintf(stderr, "Error: Memory allocation failed\n");
return ERR_RDSH_COMMUNICATION;
}
while (1) {
// Send the prompt before reading input
send_message_string(cli_socket, SH_PROMPT);
// Step 2: Receive command from client
recv_size = recv(cli_socket, io_buff, RDSH_COMM_BUFF_SZ - 1, 0);
if (recv_size < 0) {
perror("Error receiving command from client");
fprintf(stderr, CMD_ERR_RDSH_COMM);
free(io_buff);
return ERR_RDSH_COMMUNICATION;
}
// Step 3: Check for client disconnection
if (recv_size == 0) {
printf("Client disconnected\n");
free(io_buff);
return OK;
}
// Ensure null termination of received data
io_buff[recv_size] = '\0';
printf(RCMD_MSG_SVR_EXEC_REQ, io_buff);
// Step 4: Check for built-in commands
if (strcmp(io_buff, "exit") == 0) {
send_message_string(cli_socket, RCMD_MSG_CLIENT_EXITED "\n");
free(io_buff);
return OK;
}
if (strcmp(io_buff, "stop-server") == 0) {
send_message_string(cli_socket, "dsh4> stop-server\n" RCMD_MSG_SVR_STOP_REQ "\n");
fflush(stdout);
printf("stopping ...");
usleep(200000);
free(io_buff);
printf("stopping ...");
return OK_EXIT; }
// Step 5: Parse and execute the command pipeline
command_list_t clist;
rc = build_cmd_list(io_buff, &clist);
if (rc != OK) {
send_message_string(cli_socket, CMD_ERR_RDSH_EXEC);
} else {
rc = rsh_execute_pipeline(cli_socket, &clist);
free_cmd_list(&clist);
}
// Step 6: Send EOF character to mark end of response
send_message_eof(cli_socket);
}
// Cleanup before exiting
free(io_buff);
return OK;
//return WARN_RDSH_NOT_IMPL;
}
/*
* send_message_eof(cli_socket)
* cli_socket: The server-side socket that is connected to the client
* Sends the EOF character to the client to indicate that the server is
* finished executing the command that it sent.
*
* Returns:
*
* OK: The EOF character was sent successfully.
*
* ERR_RDSH_COMMUNICATION: The send() socket call returned an error or if
* we were unable to send the EOF character.
*/
int send_message_eof(int cli_socket){
int bytes_sent;
// Send EOF character to client
bytes_sent = send(cli_socket, &RDSH_EOF_CHAR, 1, 0);
if (bytes_sent < 0) {
perror("Error sending EOF to client");
fprintf(stderr, CMD_ERR_RDSH_COMM);
return ERR_RDSH_COMMUNICATION;
}
return OK;
//return WARN_RDSH_NOT_IMPL;
}
/*
* send_message_string(cli_socket, char *buff)
* cli_socket: The server-side socket that is connected to the client
* buff: A C string (aka null terminated) of a message we want
* to send to the client.
*
* Sends a message to the client. Note this command executes both a send()
* to send the message and a send_message_eof() to send the EOF character to
* the client to indicate command execution terminated.
*
* Returns:
*
* OK: The message in buff followed by the EOF character was
* sent successfully.
*
* ERR_RDSH_COMMUNICATION: The send() socket call returned an error or if * we were unable to send the message followed by the EOF character.
*/
int send_message_string(int cli_socket, char *buff){
int bytes_sent, msg_length;
// Validate input
if (!buff) {
fprintf(stderr, "Error: Null buffer passed to send_message_string()\n");
return ERR_RDSH_COMMUNICATION;
}
msg_length = strlen(buff); // Get message length
// Step 1: Send the message
bytes_sent = send(cli_socket, buff, msg_length, 0);
if (bytes_sent < 0) {
perror("Error sending message to client");
fprintf(stderr, CMD_ERR_RDSH_COMM);
return ERR_RDSH_COMMUNICATION;
}
// Check for partial send
if (bytes_sent != msg_length) {
fprintf(stderr, CMD_ERR_RDSH_SEND, bytes_sent, msg_length);
return ERR_RDSH_COMMUNICATION;
}
if (msg_length == 0) {
return send_message_eof(cli_socket); // Ensure EOF is always sent
}
// Step 2: Send EOF character
return send_message_eof(cli_socket);
//return WARN_RDSH_NOT_IMPL;
}
/*
* rsh_execute_pipeline(int cli_sock, command_list_t *clist)
* cli_sock: The server-side socket that is connected to the client
* clist: The command_list_t structure that we implemented in
* the last shell.
*
* This function executes the command pipeline. It should basically be a
* replica of the execute_pipeline() function from the last deliverable.
* The only thing different is that you will be using the cli_sock as the
* main file descriptor on the first executable in the pipeline for STDIN,
* and the cli_sock for the file descriptor for STDOUT, and STDERR for the
* last executable in the pipeline. See picture below:
*
*
*┌───────────┐ ┌───────────┐
*│ cli_sock │ │ cli_sock │
*└─────┬─────┘ └────▲──▲───┘
* │ ┌──────────────┐ ┌──────────────┐ ┌──────────────┐ │ │
* │ │ Process 1 │ │ Process 2 │ │ Process N │ │ │
* │ │ │ │ │ │ │ │ │
* └───▶stdin stdout├─┬──▶│stdin stdout├─┬──▶│stdin stdout├──┘ │
* │ │ │ │ │ │ │ │ │
* │ stderr├─┘ │ stderr├─┘ │ stderr├─────┘
* └──────────────┘ └──────────────┘ └──────────────┘
* WEXITSTATUS()
* of this last
* process to get
* the return code
* for this function *
* Returns:
*
* EXIT_CODE: This function returns the exit code of the last command
* executed in the pipeline. If only one command is executed
* that value is returned. Remember, use the WEXITSTATUS()
* macro that we discussed during our fork/exec lecture to
* get this value.
*/
int rsh_execute_pipeline(int cli_sock, command_list_t *clist) {
int num_cmds = clist->num;
int prev_pipe = -1;
int fd[2];
pid_t pids[num_cmds];
for (int i = 0; i < num_cmds; i++) {
if (i < num_cmds - 1 && pipe(fd) < 0) {
perror("pipe");
fprintf(stderr, CMD_ERR_RDSH_EXEC);
return ERR_RDSH_CMD_EXEC;
}
pids[i] = fork();
if (pids[i] < 0) {
perror("fork");
fprintf(stderr, CMD_ERR_RDSH_EXEC);
return ERR_RDSH_CMD_EXEC;
}
if (pids[i] == 0) { // Child Process
if (i == 0) {
// First command: Redirect stdin from the client socket
dup2(cli_sock, STDIN_FILENO);
} else {
// Redirect stdin from the previous pipe
dup2(prev_pipe, STDIN_FILENO);
close(prev_pipe);
}
if (i < num_cmds - 1) {
// Not the last command: Redirect stdout to the pipe
dup2(fd[1], STDOUT_FILENO);
close(fd[1]);
} else {
// Last command: Redirect stdout and stderr to client socket
dup2(cli_sock, STDOUT_FILENO);
dup2(cli_sock, STDERR_FILENO);
}
// Close all open file descriptors
if (i > 0) {
close(prev_pipe);
}
if (i < num_cmds - 1) {
close(fd[0]);
close(fd[1]); // Ensure both pipe ends are closed
}
execvp(clist->commands[i].argv[0], clist->commands[i].argv);
perror("execvp failed");
fprintf(stderr, CMD_ERR_RDSH_EXEC);
exit(ERR_RDSH_CMD_EXEC);
} else { // Parent Process
if (i > 0) close(prev_pipe);
if (i < num_cmds - 1) {
prev_pipe = fd[0];
close(fd[1]);
} }
}
// Wait for all children to finish
int status;
for (int i = 0; i < num_cmds; i++) {
waitpid(pids[i], &status, 0);
}
// Send EOF to indicate command completion
send_message_eof(cli_sock);
return WEXITSTATUS(status);
//return WARN_RDSH_NOT_IMPL;
}
/************** OPTIONAL STUFF ***************/
/****
**** NOTE THAT THE FUNCTIONS BELOW ALIGN TO HOW WE CRAFTED THE SOLUTION
**** TO SEE IF A COMMAND WAS BUILT IN OR NOT. YOU CAN USE A DIFFERENT
**** STRATEGY IF YOU WANT. IF YOU CHOOSE TO DO SO PLEASE REMOVE THESE
**** FUNCTIONS AND THE PROTOTYPES FROM rshlib.h
****
*/
/*
* rsh_match_command(const char *input)
* cli_socket: The string command for a built-in command, e.g., dragon,
* cd, exit-server
*
* This optional function accepts a command string as input and returns
* one of the enumerated values from the BuiltInCmds enum as output. For
* example:
*
* Input Output
* exit BI_CMD_EXIT
* dragon BI_CMD_DRAGON
*
* This function is entirely optional to implement if you want to handle
* processing built-in commands differently in your implementation.
*
* Returns:
*
* BI_CMD_*: If the command is built-in returns one of the enumeration
* options, for example "cd" returns BI_CMD_CD
*
* BI_NOT_BI: If the command is not "built-in" the BI_NOT_BI value is
* returned.
*/
Built_In_Cmds rsh_match_command(const char *input)
{
(void)input; // Suppress unused parameter warning
return BI_NOT_IMPLEMENTED;
}
/*
* rsh_built_in_cmd(cmd_buff_t *cmd)
* cmd: The cmd_buff_t of the command, remember, this is the
* parsed version fo the command
*
* This optional function accepts a parsed cmd and then checks to see if
* the cmd is built in or not. It calls rsh_match_command to see if the
* cmd is built in or not. Note that rsh_match_command returns BI_NOT_BI
* if the command is not built in. If the command is built in this function
* uses a switch statement to handle execution if appropriate.
*
* Again, using this function is entirely optional if you are using a different
* strategy to handle built-in commands. *
* Returns:
*
* BI_NOT_BI: Indicates that the cmd provided as input is not built
* in so it should be sent to your fork/exec logic
* BI_EXECUTED: Indicates that this function handled the direct execution
* of the command and there is nothing else to do, consider
* it executed. For example the cmd of "cd" gets the value of
* BI_CMD_CD from rsh_match_command(). It then makes the libc
* call to chdir(cmd->argv[1]); and finally returns BI_EXECUTED
* BI_CMD_* Indicates that a built-in command was matched and the caller
* is responsible for executing it. For example if this function
* returns BI_CMD_STOP_SVR the caller of this function is
* responsible for stopping the server. If BI_CMD_EXIT is returned
* the caller is responsible for closing the client connection.
*
* AGAIN - THIS IS TOTALLY OPTIONAL IF YOU HAVE OR WANT TO HANDLE BUILT-IN
* COMMANDS DIFFERENTLY.
*/
Built_In_Cmds rsh_built_in_cmd(cmd_buff_t *cmd)
{
(void)cmd; // Suppress unused parameter warning
return BI_NOT_IMPLEMENTED;
}