Finish implementation

Cargo.lock

@@ -4,4 +4,4 @@ version = 3
 
 [[package]]
 name = "tftpd"
-version = "0.0.0"
+version = "0.1.0"

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tftpd"
-version = "0.0.0"
+version = "0.1.0"
 authors = ["Altuğ Bakan <mail@alt.ug>"]
 edition = "2021"
 description = "TFTP Server Daemon implemented in Rust"

src/main.rs

@@ -3,14 +3,14 @@ use tftpd::{Config, Server};
 
 fn main() {
     let config = Config::new(env::args()).unwrap_or_else(|err| {
-        eprintln!("Problem parsing arguments: {}", err);
+        eprintln!("Problem parsing arguments: {err}");
         process::exit(1)
     });
 
     let server = Server::new(&config).unwrap_or_else(|err| {
         eprintln!(
-            "Problem creating server on {}:{}: {}",
-            config.ip_address, config.port, err
+            "Problem creating server on {}:{}: {err}",
+            config.ip_address, config.port
         );
         process::exit(1)
     });

src/message.rs

@@ -7,17 +7,28 @@ use crate::packet::{ErrorCode, Opcode, Packet, TransferOption};
 
 pub struct Message;
 
+const MAX_REQUEST_PACKET_SIZE: usize = 512;
+
 impl Message {
-    pub fn send_data(socket: &UdpSocket, data: &[u8]) -> Result<(), Box<dyn Error>> {
-        let buf = [&Opcode::Data.as_bytes()[..], data].concat();
+    pub fn send_data(
+        socket: &UdpSocket,
+        block_number: u16,
+        data: &[u8],
+    ) -> Result<(), Box<dyn Error>> {
+        let buf = [
+            &Opcode::Data.as_bytes()[..],
+            &block_number.to_be_bytes(),
+            data,
+        ]
+        .concat();
 
         socket.send(&buf)?;
 
         Ok(())
     }
 
-    pub fn send_ack(socket: &UdpSocket, block: u16) -> Result<(), Box<dyn Error>> {
-        let buf = [Opcode::Ack.as_bytes(), block.to_be_bytes()].concat();
+    pub fn send_ack(socket: &UdpSocket, block_number: u16) -> Result<(), Box<dyn Error>> {
+        let buf = [Opcode::Ack.as_bytes(), block_number.to_be_bytes()].concat();
 
         socket.send(&buf)?;
 
@@ -29,16 +40,21 @@ impl Message {
         code: ErrorCode,
         msg: &str,
     ) -> Result<(), Box<dyn Error>> {
-        socket.send(&get_error_buf(code, msg))?;
+        socket.send(&build_error_buf(code, msg))?;
 
         Ok(())
     }
 
-    pub fn send_error_to(socket: &UdpSocket, to: &SocketAddr, code: ErrorCode, msg: &str) {
-        eprintln!("{msg}");
-        if socket.send_to(&get_error_buf(code, msg), to).is_err() {
+    pub fn send_error_to<'a>(
+        socket: &UdpSocket,
+        to: &SocketAddr,
+        code: ErrorCode,
+        msg: &'a str,
+    ) -> Result<(), Box<dyn Error>> {
+        if socket.send_to(&build_error_buf(code, msg), to).is_err() {
             eprintln!("could not send an error message");
         }
+        Err(msg.into())
     }
 
     pub fn send_oack(
@@ -56,19 +72,32 @@ impl Message {
         Ok(())
     }
 
-    pub fn receive_ack(socket: &UdpSocket) -> Result<u16, Box<dyn Error>> {
-        let mut buf = [0; 4];
-        socket.recv(&mut buf)?;
+    pub fn recv(socket: &UdpSocket) -> Result<Packet, Box<dyn Error>> {
+        let mut buf = [0; MAX_REQUEST_PACKET_SIZE];
+        let number_of_bytes = socket.recv(&mut buf)?;
+        let packet = Packet::deserialize(&buf[..number_of_bytes])?;
 
-        if let Ok(Packet::Ack(block)) = Packet::deserialize(&buf) {
-            Ok(block)
-        } else {
-            Err("invalid ack".into())
-        }
+        Ok(packet)
+    }
+
+    pub fn recv_data(socket: &UdpSocket, size: usize) -> Result<Packet, Box<dyn Error>> {
+        let mut buf = vec![0; size + 4];
+        let number_of_bytes = socket.recv(&mut buf)?;
+        let packet = Packet::deserialize(&buf[..number_of_bytes])?;
+
+        Ok(packet)
+    }
+
+    pub fn recv_from(socket: &UdpSocket) -> Result<(Packet, SocketAddr), Box<dyn Error>> {
+        let mut buf = [0; MAX_REQUEST_PACKET_SIZE];
+        let (number_of_bytes, from) = socket.recv_from(&mut buf)?;
+        let packet = Packet::deserialize(&buf[..number_of_bytes])?;
+
+        Ok((packet, from))
     }
 }
 
-fn get_error_buf(code: ErrorCode, msg: &str) -> Vec<u8> {
+fn build_error_buf(code: ErrorCode, msg: &str) -> Vec<u8> {
     [
         &Opcode::Error.as_bytes()[..],
         &code.as_bytes()[..],

src/packet.rs

@@ -1,7 +1,7 @@
 use crate::Convert;
-use std::error::Error;
+use std::{error::Error, fmt};
 
-pub enum Packet<'a> {
+pub enum Packet {
     Rrq {
         filename: String,
         mode: String,
@@ -14,7 +14,7 @@ pub enum Packet<'a> {
     },
     Data {
         block_num: u16,
-        data: &'a [u8],
+        data: Vec<u8>,
     },
     Ack(u16),
     Error {
@@ -23,9 +23,9 @@ pub enum Packet<'a> {
     },
 }
 
-impl<'a> Packet<'a> {
-    pub fn deserialize(buf: &'a [u8]) -> Result<Packet, Box<dyn Error>> {
-        let opcode = Opcode::from_u16(Convert::to_u16(&buf[0..1])?)?;
+impl Packet {
+    pub fn deserialize(buf: &[u8]) -> Result<Packet, Box<dyn Error>> {
+        let opcode = Opcode::from_u16(Convert::to_u16(&buf[0..=1])?)?;
 
         match opcode {
             Opcode::Rrq | Opcode::Wrq => parse_rq(buf, opcode),
@@ -66,7 +66,7 @@ impl Opcode {
     }
 }
 
-#[derive(Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub struct TransferOption {
     pub option: OptionType,
     pub value: usize,
@@ -84,7 +84,7 @@ impl TransferOption {
     }
 }
 
-#[derive(Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub enum OptionType {
     BlockSize,
     TransferSize,
@@ -100,10 +100,6 @@ impl OptionType {
         }
     }
 
-    fn as_bytes(&self) -> &[u8] {
-        self.as_str().as_bytes()
-    }
-
     fn from_str(value: &str) -> Result<Self, &'static str> {
         match value {
             "blksize" => Ok(OptionType::BlockSize),
@@ -147,6 +143,21 @@ impl ErrorCode {
     }
 }
 
+impl fmt::Display for ErrorCode {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            ErrorCode::NotDefined => write!(f, "Not Defined"),
+            ErrorCode::FileNotFound => write!(f, "File Not Found"),
+            ErrorCode::AccessViolation => write!(f, "Access Violation"),
+            ErrorCode::DiskFull => write!(f, "Disk Full"),
+            ErrorCode::IllegalOperation => write!(f, "Illegal Operation"),
+            ErrorCode::UnknownId => write!(f, "Unknown ID"),
+            ErrorCode::FileExists => write!(f, "File Exists"),
+            ErrorCode::NoSuchUser => write!(f, "No Such User"),
+        }
+    }
+}
+
 fn parse_rq(buf: &[u8], opcode: Opcode) -> Result<Packet, Box<dyn Error>> {
     let mut options = vec![];
     let filename: String;
@@ -188,7 +199,7 @@ fn parse_rq(buf: &[u8], opcode: Opcode) -> Result<Packet, Box<dyn Error>> {
 fn parse_data(buf: &[u8]) -> Result<Packet, Box<dyn Error>> {
     Ok(Packet::Data {
         block_num: Convert::to_u16(&buf[2..])?,
-        data: &buf[4..],
+        data: buf[4..].to_vec(),
     })
 }
 
@@ -239,11 +250,11 @@ mod tests {
             &[0x00],
             &"octet".as_bytes(),
             &[0x00],
-            &OptionType::TransferSize.as_bytes(),
+            &OptionType::TransferSize.as_str().as_bytes(),
             &[0x00],
             &"0".as_bytes(),
             &[0x00],
-            &OptionType::Timeout.as_bytes(),
+            &OptionType::Timeout.as_str().as_bytes(),
             &[0x00],
             &"5".as_bytes(),
             &[0x00],
@@ -311,11 +322,11 @@ mod tests {
             &[0x00],
             &"octet".as_bytes(),
             &[0x00],
-            &OptionType::TransferSize.as_bytes(),
+            &OptionType::TransferSize.as_str().as_bytes(),
             &[0x00],
             &"12341234".as_bytes(),
             &[0x00],
-            &OptionType::BlockSize.as_bytes(),
+            &OptionType::BlockSize.as_str().as_bytes(),
             &[0x00],
             &"1024".as_bytes(),
             &[0x00],

src/server.rs

@@ -2,9 +2,7 @@ use crate::packet::{ErrorCode, Packet, TransferOption};
 use crate::{Config, Message, Worker};
 use std::error::Error;
 use std::net::{SocketAddr, UdpSocket};
-use std::path::{Path, PathBuf};
-
-const MAX_REQUEST_PACKET_SIZE: usize = 512;
+use std::path::PathBuf;
 
 pub struct Server {
     socket: UdpSocket,
@@ -25,63 +23,86 @@ impl Server {
 
     pub fn listen(&self) {
         loop {
-            let mut buf = [0; MAX_REQUEST_PACKET_SIZE];
-            if let Ok((number_of_bytes, from)) = self.socket.recv_from(&mut buf) {
-                if let Ok(packet) = Packet::deserialize(&buf[..number_of_bytes]) {
-                    self.handle_packet(&packet, &from)
-                }
+            if let Ok((packet, from)) = Message::recv_from(&self.socket) {
+                match packet {
+                    Packet::Rrq {
+                        filename,
+                        mut options,
+                        ..
+                    } => match self.handle_rrq(filename.clone(), &mut options, &from) {
+                        Ok(_) => {
+                            println!("Sending {filename} to {from}");
+                        }
+                        Err(err) => eprintln!("{err}"),
+                    },
+                    Packet::Wrq {
+                        filename,
+                        mut options,
+                        ..
+                    } => match self.handle_wrq(filename.clone(), &mut options, &from) {
+                        Ok(_) => {
+                            println!("Receiving {filename} from {from}");
+                        }
+                        Err(err) => eprintln!("{err}"),
+                    },
+                    _ => {
+                        Message::send_error_to(
+                            &self.socket,
+                            &from,
+                            ErrorCode::IllegalOperation,
+                            "invalid request",
+                        )
+                        .unwrap_or_else(|err| eprintln!("{err}"));
+                    }
+                };
             }
         }
     }
 
-    fn handle_packet(&self, packet: &Packet, from: &SocketAddr) {
-        match &packet {
-            Packet::Rrq {
-                filename, options, ..
-            } => self.validate_rrq(filename, options, from),
-            Packet::Wrq {
-                filename, options, ..
-            } => self.validate_wrq(filename, options, from),
-            _ => {
-                Message::send_error_to(
-                    &self.socket,
-                    from,
-                    ErrorCode::IllegalOperation,
-                    "invalid request",
-                );
-            }
-        }
-    }
-
-    fn validate_rrq(&self, filename: &String, options: &Vec<TransferOption>, to: &SocketAddr) {
-        match self.check_file_exists(&Path::new(&filename)) {
+    fn handle_rrq(
+        &self,
+        filename: String,
+        options: &mut Vec<TransferOption>,
+        to: &SocketAddr,
+    ) -> Result<(), Box<dyn Error>> {
+        match check_file_exists(&get_full_path(&filename, &self.directory), &self.directory) {
             ErrorCode::FileNotFound => {
-                Message::send_error_to(
+                return Message::send_error_to(
                     &self.socket,
                     to,
                     ErrorCode::FileNotFound,
-                    "requested file does not exist",
+                    "file does not exist",
                 );
             }
             ErrorCode::AccessViolation => {
-                Message::send_error_to(
+                return Message::send_error_to(
                     &self.socket,
                     to,
                     ErrorCode::AccessViolation,
-                    "requested file is not in the directory",
+                    "file access violation",
                 );
             }
-            ErrorCode::FileExists => self
-                .handle_rrq(filename, options, to)
-                .unwrap_or_else(|err| eprintln!("could not handle read request: {err}")),
+            ErrorCode::FileExists => Worker::send(
+                self.socket.local_addr().unwrap(),
+                *to,
+                filename,
+                options.to_vec(),
+            ),
             _ => {}
         }
+
+        Ok(())
     }
 
-    fn validate_wrq(&self, filename: &String, options: &Vec<TransferOption>, to: &SocketAddr) {
-        match self.check_file_exists(&Path::new(&filename)) {
+    fn handle_wrq(
+        &self,
+        filename: String,
+        options: &mut Vec<TransferOption>,
+        to: &SocketAddr,
+    ) -> Result<(), Box<dyn Error>> {
+        match check_file_exists(&get_full_path(&filename, &self.directory), &self.directory) {
             ErrorCode::FileExists => {
-                Message::send_error_to(
+                return Message::send_error_to(
                     &self.socket,
                     to,
                     ErrorCode::FileExists,
@@ -89,53 +110,85 @@ impl Server {
                 );
             }
             ErrorCode::AccessViolation => {
-                Message::send_error_to(
+                return Message::send_error_to(
                     &self.socket,
                     to,
                     ErrorCode::AccessViolation,
-                    "requested file is not in the directory",
+                    "file access violation",
                 );
             }
-            ErrorCode::FileNotFound => self
-                .handle_wrq(filename, options, to)
-                .unwrap_or_else(|err| eprintln!("could not handle write request: {err}")),
+            ErrorCode::FileNotFound => Worker::receive(
+                self.socket.local_addr().unwrap(),
+                *to,
+                filename,
+                options.to_vec(),
+            ),
             _ => {}
         };
-    }
-
-    fn handle_rrq(
-        &self,
-        filename: &String,
-        options: &Vec<TransferOption>,
-        to: &SocketAddr,
-    ) -> Result<(), Box<dyn Error>> {
-        let mut worker = Worker::new(&self.socket.local_addr().unwrap(), to)?;
-        worker.send_file(Path::new(&filename), options)?;
 
         Ok(())
     }
-
-    fn handle_wrq(
-        &self,
-        filename: &String,
-        options: &Vec<TransferOption>,
-        to: &SocketAddr,
-    ) -> Result<(), Box<dyn Error>> {
-        let mut worker = Worker::new(&self.socket.local_addr().unwrap(), to)?;
-        worker.receive_file(Path::new(&filename), options)?;
-
-        Ok(())
-    }
-
-    fn check_file_exists(&self, file: &Path) -> ErrorCode {
-        if !file.ancestors().any(|a| a == &self.directory) {
-            return ErrorCode::AccessViolation;
-        }
-
-        if !file.exists() {
-            return ErrorCode::FileNotFound;
-        }
-
-        ErrorCode::FileExists
-    }
+}
+
+fn check_file_exists(file: &PathBuf, directory: &PathBuf) -> ErrorCode {
+    if !validate_file_path(file, directory) {
+        return ErrorCode::AccessViolation;
+    }
+
+    if !file.exists() {
+        return ErrorCode::FileNotFound;
+    }
+
+    ErrorCode::FileExists
+}
+
+fn validate_file_path(file: &PathBuf, directory: &PathBuf) -> bool {
+    !file.to_str().unwrap().contains("..") && file.ancestors().any(|a| a == directory)
+}
+
+fn get_full_path(filename: &str, directory: &PathBuf) -> PathBuf {
+    let mut file = directory.clone();
+    file.push(PathBuf::from(filename));
+    file
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn gets_full_path() {
+        assert_eq!(
+            get_full_path("test.txt", &PathBuf::from("/dir/test")),
+            PathBuf::from("/dir/test/test.txt")
+        );
+
+        assert_eq!(
+            get_full_path("some_dir/test.txt", &PathBuf::from("/dir/test")),
+            PathBuf::from("/dir/test/some_dir/test.txt")
+        );
+    }
+
+    #[test]
+    fn validates_file_path() {
+        assert!(validate_file_path(
+            &PathBuf::from("/dir/test/file"),
+            &PathBuf::from("/dir/test")
+        ));
+
+        assert!(!validate_file_path(
+            &PathBuf::from("/system/data.txt"),
+            &PathBuf::from("/dir/test")
+        ));
+
+        assert!(!validate_file_path(
+            &PathBuf::from("~/some_data.txt"),
+            &PathBuf::from("/dir/test")
+        ));
+
+        assert!(!validate_file_path(
+            &PathBuf::from("/dir/test/../file"),
+            &PathBuf::from("/dir/test")
+        ));
+    }
 }

src/worker.rs

@@ -1,111 +1,242 @@
 use std::{
     error::Error,
     fs::File,
-    io::Read,
+    io::{Read, Write},
     net::{SocketAddr, UdpSocket},
     path::Path,
+    thread,
     time::Duration,
 };
 
 use crate::{
-    packet::{OptionType, TransferOption},
+    packet::{ErrorCode, OptionType, Packet, TransferOption},
     Message,
 };
 
-pub struct Worker {
-    socket: UdpSocket,
+pub struct Worker;
+
+pub struct WorkerOptions {
     blk_size: usize,
     t_size: usize,
-    timeout: usize,
+    timeout: u64,
+}
+
+#[derive(PartialEq, Eq)]
+enum WorkType {
+    Receive,
+    Send(u64),
 }
 
 const MAX_RETRIES: u32 = 6;
+const DEFAULT_TIMEOUT_SECS: u64 = 5;
+const DEFAULT_BLOCK_SIZE: usize = 512;
 
 impl Worker {
-    pub fn new(addr: &SocketAddr, remote: &SocketAddr) -> Result<Worker, Box<dyn Error>> {
-        let socket = UdpSocket::bind(SocketAddr::from((addr.ip(), 0)))?;
-        socket.connect(remote)?;
-        Ok(Worker {
-            socket,
-            blk_size: 512,
-            t_size: 0,
-            timeout: 5,
-        })
+    pub fn send(
+        addr: SocketAddr,
+        remote: SocketAddr,
+        filename: String,
+        mut options: Vec<TransferOption>,
+    ) {
+        thread::spawn(move || {
+            let mut handle_send = || -> Result<(), Box<dyn Error>> {
+                let socket = setup_socket(&addr, &remote)?;
+                let work_type = WorkType::Send(Path::new(&filename).metadata().unwrap().len());
+                let worker_options = parse_options(&mut options, &work_type)?;
+                send_oack(&socket, &options, &work_type)?;
+                send_file(&socket, &worker_options, &filename, &mut options)?;
+
+                Ok(())
+            };
+
+            if let Err(err) = handle_send() {
+                eprintln!("{err}");
+            }
+        });
     }
 
-    pub fn send_file(
-        &mut self,
-        file: &Path,
-        options: &Vec<TransferOption>,
-    ) -> Result<(), Box<dyn Error>> {
-        let mut file = File::open(file).unwrap();
+    pub fn receive(
+        addr: SocketAddr,
+        remote: SocketAddr,
+        filename: String,
+        mut options: Vec<TransferOption>,
+    ) {
+        thread::spawn(move || {
+            let mut handle_receive = || -> Result<(), Box<dyn Error>> {
+                let socket = setup_socket(&addr, &remote)?;
+                let work_type = WorkType::Receive;
+                let worker_options = parse_options(&mut options, &work_type)?;
+                send_oack(&socket, &options, &work_type)?;
+                receive_file(&socket, &worker_options, &filename, &mut options)?;
 
-        self.parse_options(options, Some(&file));
-        Message::send_oack(&self.socket, options)?;
+                Ok(())
+            };
 
-        self.socket
-            .set_write_timeout(Some(Duration::from_secs(self.timeout as u64)))?;
+            if let Err(err) = handle_receive() {
+                eprintln!("{err}");
+            }
+        });
+    }
+}
+
+fn send_file(
+    socket: &UdpSocket,
+    worker_options: &WorkerOptions,
+    filename: &String,
+    options: &mut Vec<TransferOption>,
+) -> Result<(), Box<dyn Error>> {
+    let mut file = File::open(filename).unwrap();
+
+    parse_options(options, &WorkType::Send(file.metadata().unwrap().len()))?;
+
+    let mut block_number = 1;
+    loop {
+        let mut chunk = vec![0; worker_options.blk_size];
+        let size = file.read(&mut chunk)?;
 
         let mut retry_cnt = 0;
         loop {
-            let mut chunk = Vec::with_capacity(self.blk_size);
-            let size = file
-                .by_ref()
-                .take(self.blk_size as u64)
-                .read_to_end(&mut chunk)?;
+            Message::send_data(socket, block_number, &chunk[..size])?;
 
-            loop {
-                if Message::send_data(&self.socket, &chunk).is_err() {
-                    return Err(format!("failed to send data").into());
+            match Message::recv(socket) {
+                Ok(Packet::Ack(received_block_number)) => {
+                    if received_block_number == block_number {
+                        block_number = block_number.wrapping_add(1);
+                        break;
+                    }
                 }
-
-                if let Ok(block) = Message::receive_ack(&self.socket) {
-                    todo!("handle block number");
-                } else {
+                Ok(Packet::Error { code, msg }) => {
+                    return Err(format!("received error code {code}, with message {msg}").into());
+                }
+                _ => {
                     retry_cnt += 1;
                     if retry_cnt == MAX_RETRIES {
                         return Err(format!("transfer timed out after {MAX_RETRIES} tries").into());
                     }
                 }
             }
-
-            if size < self.blk_size {
-                break;
-            };
         }
 
-        Ok(())
+        if size < worker_options.blk_size {
+            break;
+        };
     }
 
-    pub fn receive_file(
-        &mut self,
-        file: &Path,
-        options: &Vec<TransferOption>,
-    ) -> Result<(), Box<dyn Error>> {
-        let mut file = File::open(file).unwrap();
+    println!("Sent {filename} to {}", socket.peer_addr().unwrap());
+    Ok(())
+}
 
-        self.parse_options(options, Some(&file));
-        Message::send_oack(&self.socket, options)?;
+fn receive_file(
+    socket: &UdpSocket,
+    worker_options: &WorkerOptions,
+    filename: &String,
+    options: &mut Vec<TransferOption>,
+) -> Result<(), Box<dyn Error>> {
+    let mut file = File::create(filename).unwrap();
 
-        todo!("file receiving");
+    parse_options(options, &WorkType::Receive)?;
 
-        Ok(())
-    }
+    let mut block_number: u16 = 0;
+    loop {
+        let size;
 
-    fn parse_options(&mut self, options: &Vec<TransferOption>, file: Option<&File>) {
-        for option in options {
-            let TransferOption { option, value } = option;
-
-            match option {
-                OptionType::BlockSize => self.blk_size = *value,
-                OptionType::TransferSize => {
-                    self.t_size = match file {
-                        Some(file) => file.metadata().unwrap().len() as usize,
-                        None => *value,
+        let mut retry_cnt = 0;
+        loop {
+            match Message::recv_data(socket, worker_options.blk_size) {
+                Ok(Packet::Data {
+                    block_num: received_block_number,
+                    data,
+                }) => {
+                    if received_block_number == block_number.wrapping_add(1) {
+                        block_number = received_block_number;
+                        file.write(&data)?;
+                        size = data.len();
+                        break;
                     }
                 }
-                OptionType::Timeout => self.timeout = *value,
+                Ok(Packet::Error { code, msg }) => {
+                    return Err(format!("received error code {code}: {msg}").into());
+                }
+                Err(err) => {
+                    retry_cnt += 1;
+                    if retry_cnt == MAX_RETRIES {
+                        return Err(
+                            format!("transfer timed out after {MAX_RETRIES} tries: {err}").into(),
+                        );
+                    }
+                }
+                _ => {}
+            }
+        }
+
+        Message::send_ack(socket, block_number)?;
+        if size < worker_options.blk_size {
+            break;
+        };
+    }
+
+    println!("Received {filename} from {}", socket.peer_addr().unwrap());
+    Ok(())
+}
+
+fn setup_socket(addr: &SocketAddr, remote: &SocketAddr) -> Result<UdpSocket, Box<dyn Error>> {
+    let socket = UdpSocket::bind(SocketAddr::from((addr.ip(), 0)))?;
+    socket.connect(remote)?;
+    socket.set_read_timeout(Some(Duration::from_secs(DEFAULT_TIMEOUT_SECS)))?;
+    socket.set_write_timeout(Some(Duration::from_secs(DEFAULT_TIMEOUT_SECS)))?;
+    Ok(socket)
+}
+
+fn parse_options(
+    options: &mut Vec<TransferOption>,
+    work_type: &WorkType,
+) -> Result<WorkerOptions, Box<dyn Error>> {
+    let mut worker_options = WorkerOptions {
+        blk_size: DEFAULT_BLOCK_SIZE,
+        t_size: 0,
+        timeout: DEFAULT_TIMEOUT_SECS,
+    };
+
+    for option in &mut *options {
+        let TransferOption { option, value } = option;
+
+        match option {
+            OptionType::BlockSize => worker_options.blk_size = *value,
+            OptionType::TransferSize => match work_type {
+                WorkType::Send(size) => {
+                    *value = *size as usize;
+                }
+                WorkType::Receive => {
+                    worker_options.t_size = *value;
+                }
+            },
+            OptionType::Timeout => {
+                if *value == 0 {
+                    return Err("invalid timeout value".into());
+                }
+                worker_options.timeout = *value as u64;
             }
         }
     }
+
+    Ok(worker_options)
+}
+
+fn send_oack(
+    socket: &UdpSocket,
+    options: &Vec<TransferOption>,
+    work_type: &WorkType,
+) -> Result<(), Box<dyn Error>> {
+    if options.len() > 0 {
+        Message::send_oack(socket, options)?;
+        if let Packet::Ack(received_block_number) = Message::recv(socket)? {
+            if received_block_number != 0 {
+                Message::send_error(socket, ErrorCode::IllegalOperation, "invalid oack response")?;
+            }
+        }
+    } else if *work_type == WorkType::Receive {
+        Message::send_ack(socket, 0)?
+    }
+
+    Ok(())
 }