diff --git a/common_service/ruxfdtab/src/as_apis.rs b/common_service/ruxfdtab/src/as_apis.rs
index 71dcf198..dd8fca14 100644
--- a/common_service/ruxfdtab/src/as_apis.rs
+++ b/common_service/ruxfdtab/src/as_apis.rs
@@ -3,8 +3,7 @@ extern crate alloc;
 use std::path::PathBuf;
 
 use alloc::vec;
-use ms_std::{libos::libos, sync::UPSafeCell};
-use spin::Mutex;
+use ms_std::{libos::libos};
 
 use crate::{
     fd_ops::{close_file_like, get_file_like},
@@ -21,6 +20,8 @@ use ruxdriver::init_drivers;
 use ruxfs::init_blkfs;
 
 use ruxfdtable::{FileLike, RuxStat};
+
+#[allow(unused_imports)]
 use ruxfs::{fops::OpenOptions, init_filesystems, init_tempfs, prepare_commonfs};
 
 fn convert(ruxstat: RuxStat) -> Stat {
diff --git a/libmsvisor/src/isolation/config.rs b/libmsvisor/src/isolation/config.rs
index 11a54a86..a7ffd86b 100644
--- a/libmsvisor/src/isolation/config.rs
+++ b/libmsvisor/src/isolation/config.rs
@@ -3,6 +3,7 @@ use std::{collections::BTreeMap, fs, io::BufReader, path::PathBuf};
 use anyhow;
 use log::{debug, warn};
 use ms_hostcall::types::ServiceName;
+#[allow(unused_imports)]
 use serde::{Deserialize, Serialize};
 
 use std::io;
diff --git a/ms_std/src/fs.rs b/ms_std/src/fs.rs
index 1392add6..099be913 100644
--- a/ms_std/src/fs.rs
+++ b/ms_std/src/fs.rs
@@ -6,7 +6,6 @@ use ms_hostcall::{
 use crate::{
     io::{Read, Write},
     libos::libos,
-    println,
 };
 
 pub struct File {
@@ -47,15 +46,15 @@ impl File {
     pub fn metadata(&self) -> FdtabResult<Stat> {
         libos!(stat(self.raw_fd))
     }
+
+    pub fn write_str(&mut self, s: &str) -> core::fmt::Result {
+        self.write_all(s.as_bytes()).map_err(|_| core::fmt::Error)
+    }
 }
 
 impl Write for File {
-    fn write_str(&mut self, s: &str) -> core::fmt::Result {
-        if libos!(write(self.raw_fd, s.as_bytes())).is_err() {
-            Err(core::fmt::Error)?
-        }
-
-        Ok(())
+    fn write(&mut self, buf: &[u8]) -> Result<usize, FdtabError> {
+        libos!(write(self.raw_fd, buf))
     }
 }
 
diff --git a/ms_std/src/io.rs b/ms_std/src/io.rs
index 254181f3..2661a0e0 100644
--- a/ms_std/src/io.rs
+++ b/ms_std/src/io.rs
@@ -1,5 +1,3 @@
-pub use core::fmt::Write;
-
 use alloc::{
     string::{String, ToString},
     vec::Vec,
@@ -34,3 +32,20 @@ pub trait Read {
         Ok(buf.len())
     }
 }
+
+pub trait Write {
+    fn write(&mut self, buf: &[u8]) -> Result<usize, FdtabError>;
+
+    fn write_all(&mut self, mut buf: &[u8]) -> Result<(), FdtabError> {
+        while !buf.is_empty() {
+            match self.write(buf) {
+                Ok(0) => {
+                    panic!("write data failed")
+                }
+                Ok(n) => buf = &buf[n..],
+                Err(e) => return Err(e),
+            }
+        }
+        Ok(())
+    }
+}
diff --git a/ms_std/src/net.rs b/ms_std/src/net.rs
index 658d1db9..056855aa 100644
--- a/ms_std/src/net.rs
+++ b/ms_std/src/net.rs
@@ -4,19 +4,22 @@ use core::{
 };
 
 use alloc::vec::Vec;
-use ms_hostcall::{fdtab::FdtabError, types::Fd};
+use ms_hostcall::{fdtab::FdtabError, socket::SmoltcpError, types::Fd};
 
-use crate::{io::Write, libos::libos};
+use crate::{
+    io::{Read, Write},
+    libos::libos,
+};
 
 pub struct TcpStream {
     raw_fd: Fd,
 }
 
 impl TcpStream {
-    pub fn connect(addr: SocketAddr) -> Result<Self, FdtabError> {
+    pub fn connect<A: ToSocketAddrs>(addr: A) -> Result<Self, FdtabError> {
         // println!("connect to {}", addr);
 
-        let sockaddrv4 = match addr.inner {
+        let sockaddrv4 = match addr.to_socket_addrs()?.inner {
             core::net::SocketAddr::V4(addr) => addr,
             core::net::SocketAddr::V6(_) => todo!(),
         };
@@ -26,20 +29,20 @@ impl TcpStream {
         Ok(stream)
     }
 
-    pub fn write_all(&mut self, data: &[u8]) -> Result<(), FdtabError> {
-        let _ = libos!(write(self.raw_fd, data))?;
-        // println!("TcpStream write {} bytes.", data.len());
-        Ok(())
-    }
+    // fn write_str(&mut self, s: &str) -> core::fmt::Result {
+    //     self.write_all(s.as_bytes()).map_err(|_| core::fmt::Error)
+    // }
+}
 
-    pub fn read(&mut self, buf: &mut [u8]) -> Result<usize, FdtabError> {
-        libos!(read(self.raw_fd, buf))
+impl Write for TcpStream {
+    fn write(&mut self, buf: &[u8]) -> Result<usize, FdtabError> {
+        libos!(write(self.raw_fd, buf))
     }
 }
 
-impl Write for TcpStream {
-    fn write_str(&mut self, s: &str) -> core::fmt::Result {
-        self.write_all(s.as_bytes()).map_err(|_| core::fmt::Error)
+impl Read for TcpStream {
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize, FdtabError> {
+        libos!(read(self.raw_fd, buf))
     }
 }
 
@@ -68,8 +71,8 @@ pub struct TcpListener {
 }
 
 impl TcpListener {
-    pub fn bind(url: &str) -> Result<Self, FdtabError> {
-        let addr: SocketAddr = url.into();
+    pub fn bind<A: ToSocketAddrs>(url: A) -> Result<Self, FdtabError> {
+        let addr: SocketAddr = url.to_socket_addrs().unwrap();
         let sockaddrv4 = match addr.inner {
             core::net::SocketAddr::V4(addr) => addr,
             core::net::SocketAddr::V6(_) => todo!(),
@@ -106,12 +109,16 @@ impl Display for SocketAddr {
     }
 }
 
-impl From<&str> for SocketAddr {
-    fn from(value: &str) -> Self {
+pub trait ToSocketAddrs {
+    fn to_socket_addrs(&self) -> Result<SocketAddr, SmoltcpError>;
+}
+
+impl ToSocketAddrs for &str {
+    fn to_socket_addrs(&self) -> Result<SocketAddr, SmoltcpError> {
         let mut sockaddr = SocketAddr::default();
 
         let (ip, port) = {
-            let target_tuple: Vec<&str> = value.split(':').collect();
+            let target_tuple: Vec<&str> = self.split(':').collect();
             let host_str = target_tuple[0];
             let addr = if let Ok(addr) = host_str.parse() {
                 addr
@@ -129,6 +136,6 @@ impl From<&str> for SocketAddr {
 
         sockaddr.inner = core::net::SocketAddr::from(SocketAddrV4::new(ip, port));
 
-        sockaddr
+        Ok(sockaddr)
     }
 }
diff --git a/ms_std/src/prelude.rs b/ms_std/src/prelude.rs
index 6453e33d..1532b9c9 100644
--- a/ms_std/src/prelude.rs
+++ b/ms_std/src/prelude.rs
@@ -1,3 +1,5 @@
 pub extern crate alloc;
 pub use crate::agent::{DataBuffer, FaaSFuncResult as Result};
 pub use crate::println;
+
+pub use alloc::string::String;
diff --git a/scripts/build_user.sh b/scripts/build_user.sh
index 44f9bcce..04fe6007 100755
--- a/scripts/build_user.sh
+++ b/scripts/build_user.sh
@@ -25,6 +25,7 @@ for file in $(find user -name 'Cargo.toml' \
     -not -path 'user/never_stop/Cargo.toml' \
     -not -path 'user/tinywasm*/Cargo.toml' \
     -not -path 'user/wasmtime*/Cargo.toml'); do
+    echo "Build $file".
     if ! bash -c "cargo build $feature_arg --manifest-path $file $release_flag"; then
         echo "Build $file failed!"
         exit 1
diff --git a/user/file_reader/src/lib.rs b/user/file_reader/src/lib.rs
index eee684ce..1d75dba4 100644
--- a/user/file_reader/src/lib.rs
+++ b/user/file_reader/src/lib.rs
@@ -10,6 +10,7 @@ use ms_std::{
     time::{SystemTime, UNIX_EPOCH},
 };
 use ms_std_proc_macro::FaasData;
+#[allow(unused_imports)]
 use serde::{Deserialize, Serialize};
 // use ms_std_proc_macro::FaasData;
 
diff --git a/user/func_a/src/lib.rs b/user/func_a/src/lib.rs
index 34a291eb..d9a2fec9 100644
--- a/user/func_a/src/lib.rs
+++ b/user/func_a/src/lib.rs
@@ -3,6 +3,8 @@
 extern crate alloc;
 
 use alloc::{borrow::ToOwned, vec::Vec};
+
+#[allow(unused_imports)]
 use ms_std::{
     agent::{DataBuffer, FaaSFuncResult as Result},
     println,
diff --git a/user/load_all/src/lib.rs b/user/load_all/src/lib.rs
index fcd73324..bf7eb7cb 100644
--- a/user/load_all/src/lib.rs
+++ b/user/load_all/src/lib.rs
@@ -4,7 +4,7 @@ use ms_std::args;
 
 cfg_if::cfg_if! {
     if #[cfg(feature = "with_libos")] {
-        use ms_std::{agent::FaaSFuncResult as Result, println, libos::libos, fs::File};
+        use ms_std::{agent::FaaSFuncResult as Result, println, libos::libos};
         extern crate alloc;
     } else {
         type Result<T> = core::result::Result<T, String>;
diff --git a/user/mapper/src/lib.rs b/user/mapper/src/lib.rs
index 9468897b..17ca2607 100644
--- a/user/mapper/src/lib.rs
+++ b/user/mapper/src/lib.rs
@@ -1,5 +1,6 @@
 #![no_std]
 
+#[allow(unused_imports)]
 use core::str::FromStr;
 
 use alloc::{
@@ -20,9 +21,11 @@ use ms_std::{
     fs::File,
     io::Read,
     println,
-    time::{SystemTime, UNIX_EPOCH},
+    time::{SystemTime},
 };
 use ms_std_proc_macro::FaasData;
+
+#[allow(unused_imports)]
 use serde::{Deserialize, Serialize};
 
 extern crate alloc;
diff --git a/user/merger/src/lib.rs b/user/merger/src/lib.rs
index 59e7c2a6..0277dbdb 100644
--- a/user/merger/src/lib.rs
+++ b/user/merger/src/lib.rs
@@ -7,6 +7,8 @@ use ms_std::{
     time::{SystemTime, UNIX_EPOCH},
 };
 use ms_std_proc_macro::FaasData;
+
+#[allow(unused_imports)]
 use serde::{Deserialize, Serialize};
 
 #[cfg(feature = "pkey_per_func")]
@@ -74,6 +76,7 @@ fn merge_partitions(partitions: Vec<&NumberArray>, dst: &mut NumberArray) {
 
         match min_partition {
             Some(partition_idx) => {
+                #[allow(unused_variables)]
                 let ret = dst.push(min_value);
                 #[cfg(feature = "pkey_per_func")]
                 {
diff --git a/user/reducer/src/lib.rs b/user/reducer/src/lib.rs
index 8195ce80..6da233c1 100644
--- a/user/reducer/src/lib.rs
+++ b/user/reducer/src/lib.rs
@@ -1,4 +1,6 @@
 #![no_std]
+
+#[allow(unused_imports)]
 use core::str::FromStr;
 
 use alloc::{
@@ -14,6 +16,8 @@ use ms_std::{
     time::{SystemTime, UNIX_EPOCH},
 };
 use ms_std_proc_macro::FaasData;
+
+#[allow(unused_imports)]
 use serde::{Deserialize, Serialize};
 
 extern crate alloc;
diff --git a/user/simple_file/src/lib.rs b/user/simple_file/src/lib.rs
index 295ca39e..efd66425 100644
--- a/user/simple_file/src/lib.rs
+++ b/user/simple_file/src/lib.rs
@@ -6,6 +6,8 @@ use alloc::{
     string::{String, ToString},
     vec::Vec,
 };
+
+#[allow(unused_imports)]
 use ms_std::{
     agent::FaaSFuncResult as Result,
     fs::File,
@@ -85,13 +87,13 @@ use ms_std::{
 
 #[no_mangle]
 pub fn main() -> Result<()> {
-    let start_time = SystemTime::now();
+    // let start_time = SystemTime::now();
     let path = "lines.txt";
 
     /////////////////// test create/write/read. ///////////////////
     let data = "Rust LibOS Cool.";
     let mut output = File::create(path)?;
-    write!(output, "{}", data).expect("");
+    output.write_str(data).expect("");
     // drop(output);
 
     let mut input_file = File::open(path)?;
diff --git a/user/simple_http/src/lib.rs b/user/simple_http/src/lib.rs
index d13d5e79..03fff5c2 100644
--- a/user/simple_http/src/lib.rs
+++ b/user/simple_http/src/lib.rs
@@ -1,15 +1,15 @@
 #![no_std]
 #![allow(clippy::result_unit_err)]
 
-extern crate alloc;
-
-use alloc::string::String;
-
-use ms_std::{agent::FaaSFuncResult as Result, net::TcpStream, println};
+use ms_std::{
+    io::{Read, Write},
+    net::TcpStream,
+    prelude::*,
+};
 
 #[no_mangle]
 pub fn main() -> Result<()> {
-    let mut stream = TcpStream::connect("www.baidu.com".into())?;
+    let mut stream = TcpStream::connect("example.com")?;
     println!("tcp connection created.");
     stream.write_all(b"GET / HTTP/1.0\r\n\r\n")?;
     let mut buffer = [0; 4096];
diff --git a/user/sorter/src/lib.rs b/user/sorter/src/lib.rs
index ccf7837b..e918b388 100644
--- a/user/sorter/src/lib.rs
+++ b/user/sorter/src/lib.rs
@@ -2,6 +2,8 @@
 
 use alloc::{format, string::String, vec::Vec};
 
+
+#[allow(unused_imports)]
 use ms_std::{
     args,
     fs::File,
@@ -10,6 +12,8 @@ use ms_std::{
     time::{SystemTime, UNIX_EPOCH},
 };
 use ms_std_proc_macro::FaasData;
+
+#[allow(unused_imports)]
 use serde::{Deserialize, Serialize};
 
 #[cfg_attr(feature = "file-based", derive(Serialize, Deserialize))]
diff --git a/user/splitter/src/lib.rs b/user/splitter/src/lib.rs
index 2fd8e134..c2b52e2d 100644
--- a/user/splitter/src/lib.rs
+++ b/user/splitter/src/lib.rs
@@ -8,6 +8,8 @@ use ms_std::{
     time::{SystemTime, UNIX_EPOCH},
 };
 use ms_std_proc_macro::FaasData;
+
+#[allow(unused_imports)]
 use serde::{Deserialize, Serialize};
 
 #[cfg_attr(feature = "file-based", derive(Serialize, Deserialize))]