Is there a buffered tcp stream in ASIO?

|Prepare a tcp server listening on [::]:23380, run the following code:

#include <boost/asio.hpp>

namespace io = boost::asio;
using boost::system::system_error;

int main() {
     try {
         io::io_context ctx;
         using io::ip::tcp;
         using io::buffer;
         tcp::socket s1(ctx);
         s1.connect(tcp::endpoint(io::ip::address_v4::loopback(), 23380));
         for (size_t i{}; i != 10; ++i)
             io::write(s1, buffer("123", 3));
     } catch (system_error& e) {
         return 1;
     }
}

strace says there are 10 syscalls:

connect(6, {sa_family=AF_INET, sin_port=htons(23380), 
sin_addr=inet_addr("127.0.0.1")}, 16) = 0
sendto(6, "123", 3, MSG_NOSIGNAL, NULL, 0) = 3
sendto(6, "123", 3, MSG_NOSIGNAL, NULL, 0) = 3
sendto(6, "123", 3, MSG_NOSIGNAL, NULL, 0) = 3
sendto(6, "123", 3, MSG_NOSIGNAL, NULL, 0) = 3
sendto(6, "123", 3, MSG_NOSIGNAL, NULL, 0) = 3
sendto(6, "123", 3, MSG_NOSIGNAL, NULL, 0) = 3
sendto(6, "123", 3, MSG_NOSIGNAL, NULL, 0) = 3
sendto(6, "123", 3, MSG_NOSIGNAL, NULL, 0) = 3
sendto(6, "123", 3, MSG_NOSIGNAL, NULL, 0) = 3
sendto(6, "123", 3, MSG_NOSIGNAL, NULL, 0) = 3

If I use boost::asio::ip::tcp::iostream:

#include <boost/asio.hpp>

namespace io = boost::asio;
using boost::system::system_error;

int main() {
     try {
         io::io_context ctx;
         using io::ip::tcp;
         using io::buffer;
         tcp::iostream s1{ tcp::socket(ctx) };
         auto& nl = s1.socket();
         nl.connect(tcp::endpoint(io::ip::address_v4::loopback(), 23380));
         for (size_t i{}; i != 10; ++i)
             s1.write("123", 3);
         s1.flush();
     } catch (system_error& e) {
         return 1;
     }
}

It does not make sense, still 10 syscalls:

connect(6, {sa_family=AF_INET, sin_port=htons(23380), 
sin_addr=inet_addr("127.0.0.1")}, 16) = 0
ioctl(6, FIONBIO, [1])                  = 0
sendmsg(6, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="123", 
iov_len=3}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 3
sendmsg(6, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="123", 
iov_len=3}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 3
sendmsg(6, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="123", 
iov_len=3}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 3
sendmsg(6, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="123", 
iov_len=3}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 3
sendmsg(6, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="123", 
iov_len=3}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 3
sendmsg(6, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="123", 
iov_len=3}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 3
sendmsg(6, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="123", 
iov_len=3}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 3
sendmsg(6, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="123", 
iov_len=3}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 3
sendmsg(6, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="123", 
iov_len=3}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 3
sendmsg(6, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="123", 
iov_len=3}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 3

Is there a stream in asio that could buffer the multiple and small 
pieces of data into one syscall?

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