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