tcp_client.h

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// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)
 
#pragma once
 
#ifdef _WIN32
#error include tcp_client-windows.h instead
#endif
 
// tcp client helper
#include <spdlog/common.h>
#include <spdlog/details/os.h>
 
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <netdb.h>
#include <netinet/tcp.h>
#include <netinet/in.h>
 
#include <string>
 
namespace spdlog
{
    namespace details
    {
        class tcp_client
        {
            int socket_ = -1;
 
        public:
            bool is_connected() const
            {
                return socket_ != -1;
            }
 
            void close()
            {
                if (is_connected())
                {
                    ::close(socket_);
                    socket_ = -1;
                }
            }
 
            int fd() const
            {
                return socket_;
            }
 
            ~tcp_client()
            {
                close();
            }
 
            // try to connect or throw on failure
            void connect(const std::string& host, int port)
            {
                close();
                struct addrinfo hints
                {
                };
                memset(&hints, 0, sizeof(struct addrinfo));
                hints.ai_family   = AF_INET;        // IPv4
                hints.ai_socktype = SOCK_STREAM;    // TCP
                hints.ai_flags    = AI_NUMERICSERV; // port passed as as numeric value
                hints.ai_protocol = 0;
 
                auto             port_str = std::to_string(port);
                struct addrinfo* addrinfo_result;
                auto             rv = ::getaddrinfo(host.c_str(), port_str.c_str(), &hints, &addrinfo_result);
                if (rv != 0)
                {
                    throw_spdlog_ex(fmt_lib::format("::getaddrinfo failed: {}", gai_strerror(rv)));
                }
 
                // Try each address until we successfully connect(2).
                int last_errno = 0;
                for (auto* rp = addrinfo_result; rp != nullptr; rp = rp->ai_next)
                {
#if defined(SOCK_CLOEXEC)
                    const int flags = SOCK_CLOEXEC;
#else
                    const int flags = 0;
#endif
                    socket_ = ::socket(rp->ai_family, rp->ai_socktype | flags, rp->ai_protocol);
                    if (socket_ == -1)
                    {
                        last_errno = errno;
                        continue;
                    }
                    rv = ::connect(socket_, rp->ai_addr, rp->ai_addrlen);
                    if (rv == 0)
                    {
                        break;
                    }
                    last_errno = errno;
                    ::close(socket_);
                    socket_ = -1;
                }
                ::freeaddrinfo(addrinfo_result);
                if (socket_ == -1)
                {
                    throw_spdlog_ex("::connect failed", last_errno);
                }
 
                // set TCP_NODELAY
                int enable_flag = 1;
                ::setsockopt(socket_, IPPROTO_TCP, TCP_NODELAY, reinterpret_cast<char*>(&enable_flag), sizeof(enable_flag));
 
                // prevent sigpipe on systems where MSG_NOSIGNAL is not available
#if defined(SO_NOSIGPIPE) && !defined(MSG_NOSIGNAL)
                ::setsockopt(socket_, SOL_SOCKET, SO_NOSIGPIPE, reinterpret_cast<char*>(&enable_flag), sizeof(enable_flag));
#endif
 
#if !defined(SO_NOSIGPIPE) && !defined(MSG_NOSIGNAL)
#error "tcp_sink would raise SIGPIPE since neither SO_NOSIGPIPE nor MSG_NOSIGNAL are available"
#endif
            }
 
            // Send exactly n_bytes of the given data.
            // On error close the connection and throw.
            void send(const char* data, size_t n_bytes)
            {
                size_t bytes_sent = 0;
                while (bytes_sent < n_bytes)
                {
#if defined(MSG_NOSIGNAL)
                    const int send_flags = MSG_NOSIGNAL;
#else
                    const int send_flags = 0;
#endif
                    auto write_result = ::send(socket_, data + bytes_sent, n_bytes - bytes_sent, send_flags);
                    if (write_result < 0)
                    {
                        close();
                        throw_spdlog_ex("write(2) failed", errno);
                    }
 
                    if (write_result == 0) // (probably should not happen but in any case..)
                    {
                        break;
                    }
                    bytes_sent += static_cast<size_t>(write_result);
                }
            }
        };
    } // namespace details
} // namespace spdlog