大约 3 分钟
同步写write_some
boost::asio提供了几种同步写的api，write_some可以每次向指定的空间写入固定的字节数，如果写缓冲区满了，就只写一部分，返回写入的字节数。
void wirte_to_socket(asio::ip::tcp::socket& sock) {
std::string buf = "Hello World!";
std::size_t total_bytes_written = 0;
//循环发送
//write_some返回每次写入的字节数
//total_bytes_written是已经发送的字节数。
//每次发送buf.length()- total_bytes_written)字节数据
while (total_bytes_written != buf.length()) {
total_bytes_written += sock.write_some(
asio::buffer(buf.c_str()+total_bytes_written,
buf.length()- total_bytes_written));
}
}
同步写send
write_some使用起来比较麻烦，需要多次调用，asio提供了send函数。send函数会一次性将buffer中的内容发送给对端，如果有部分字节因为发送缓冲区满无法发送，则阻塞等待，直到发送缓冲区可用，则继续发送完成。
int send_data_by_send(){
std::string raw_ip_address = "127.0.0.1";
unsigned short port_num = 3333;
try {
asio::ip::tcp::endpoint
ep(asio::ip::address::from_string(raw_ip_address),
port_num);
asio::io_service ios;
// Step 1. Allocating and opening the socket.
asio::ip::tcp::socket sock(ios, ep.protocol());
sock.connect(ep);
std::string buf = "Hello World!";
int send_length = sock.send(asio::buffer(buf.c_str(), buf.length()));
if (send_length <= 0) {
cout << "send failed" << endl;
return 0;
}
}
catch (system::system_error& e) {
std::cout << "Error occured! Error code = " << e.code()
<< ". Message: " << e.what();
return e.code().value();
}
return 0;
}
同步写write
类似send方法，asio还提供了一个write函数，可以一次性将所有数据发送给对端，如果发送缓冲区满了则阻塞，直到发送缓冲区可用，将数据发送完成。
int send_data_by_wirte() {
std::string raw_ip_address = "127.0.0.1";
unsigned short port_num = 3333;
try {
asio::ip::tcp::endpoint
ep(asio::ip::address::from_string(raw_ip_address),
port_num);
asio::io_service ios;
// Step 1. Allocating and opening the socket.
asio::ip::tcp::socket sock(ios, ep.protocol());
sock.connect(ep);
std::string buf = "Hello World!";
int send_length = asio::write(sock, asio::buffer(buf.c_str(), buf.length()));
if (send_length <= 0) {
cout << "send failed" << endl;
return 0;
}
}
catch (system::system_error& e) {
std::cout << "Error occured! Error code = " << e.code()
<< ". Message: " << e.what();
return e.code().value();
}
return 0;
}
同步读read_some
同步读和同步写类似，提供了读取指定字节数的接口read_some
std::string read_from_socket(asio::ip::tcp::socket& sock) {
const unsigned char MESSAGE_SIZE = 7;
char buf[MESSAGE_SIZE];
std::size_t total_bytes_read = 0;
while (total_bytes_read != MESSAGE_SIZE) {
total_bytes_read += sock.read_some(
asio::buffer(buf + total_bytes_read,
MESSAGE_SIZE - total_bytes_read));
}
return std::string(buf, total_bytes_read);
}
int read_data_by_read_some() {
std::string raw_ip_address = "127.0.0.1";
unsigned short port_num = 3333;
try {
asio::ip::tcp::endpoint
ep(asio::ip::address::from_string(raw_ip_address),
port_num);
asio::io_service ios;
asio::ip::tcp::socket sock(ios, ep.protocol());
sock.connect(ep);
read_from_socket(sock);
}
catch (system::system_error& e) {
std::cout << "Error occured! Error code = " << e.code()
<< ". Message: " << e.what();
return e.code().value();
}
return 0;
}
同步读receive
可以一次性同步接收对方发送的数据
int read_data_by_receive() {
std::string raw_ip_address = "127.0.0.1";
unsigned short port_num = 3333;
try {
asio::ip::tcp::endpoint
ep(asio::ip::address::from_string(raw_ip_address),
port_num);
asio::io_service ios;
asio::ip::tcp::socket sock(ios, ep.protocol());
sock.connect(ep);
const unsigned char BUFF_SIZE = 7;
char buffer_receive[BUFF_SIZE];
int receive_length = sock.receive(asio::buffer(buffer_receive, BUFF_SIZE));
if (receive_length <= 0) {
cout << "receive failed" << endl;
}
}
catch (system::system_error& e) {
std::cout << "Error occured! Error code = " << e.code()
<< ". Message: " << e.what();
return e.code().value();
}
return 0;
}
同步读read
可以一次性同步读取对方发送的数据
int read_data_by_read() {
std::string raw_ip_address = "127.0.0.1";
unsigned short port_num = 3333;
try {
asio::ip::tcp::endpoint
ep(asio::ip::address::from_string(raw_ip_address),
port_num);
asio::io_service ios;
asio::ip::tcp::socket sock(ios, ep.protocol());
sock.connect(ep);
const unsigned char BUFF_SIZE = 7;
char buffer_receive[BUFF_SIZE];
int receive_length = asio::read(sock, asio::buffer(buffer_receive, BUFF_SIZE));
if (receive_length <= 0) {
cout << "receive failed" << endl;
}
}
catch (system::system_error& e) {
std::cout << "Error occured! Error code = " << e.code()
<< ". Message: " << e.what();
return e.code().value();
}
return 0;
}
读取直到指定字符
我们可以一直读取，直到读取指定字符结束
std::string read_data_by_until(asio::ip::tcp::socket& sock) {
asio::streambuf buf;
// Synchronously read data from the socket until
// '\n' symbol is encountered.
asio::read_until(sock, buf, '\n');
std::string message;
// Because buffer 'buf' may contain some other data
// after '\n' symbol, we have to parse the buffer and
// extract only symbols before the delimiter.
std::istream input_stream(&buf);
std::getline(input_stream, message);
return message;
}