// Close existing connection if any

if (is_valid()) {

close();

}

auto portStr = std::to_string(port);

// Resolve via the system resolver (getaddrinfo). On Termux/Android a

// musl-static build can't — its nameservers live in $PREFIX/etc/resolv.conf

// which libc never reads — so fall back to a manual DNS query there.

auto try_resolved = [&](const char* node, bool numeric) -> bool {

struct addrinfo hints{};

hints.ai_family = AF_UNSPEC;

hints.ai_socktype = SOCK_STREAM;

hints.ai_protocol = IPPROTO_TCP;

if (numeric) hints.ai_flags = AI_NUMERICHOST;

struct addrinfo* result = nullptr;

if (::getaddrinfo(node, portStr.c_str(), &hints, &result) != 0 || result == nullptr) {

return false;

}

bool ok = connect_addrinfo(result, timeoutMs);

::freeaddrinfo(result);

return ok;

};

if constexpr (platform::is_windows) {

return try_resolved(host, /*numeric=*/false);

} else {

// Fall back to a manual DNS query when libc can't resolve (Termux:

// nameservers live in $PREFIX/etc/resolv.conf, which libc ignores).

auto try_manual = [&]() -> bool {

// DNS must be snappy: a UDP query to a working resolver answers

// in well under a second. Cap it hard (independent of the much

// larger connect timeout) so an intermittently-dropped packet to

// 8.8.8.8 can't stall a connect for tens of seconds per host.

// Plain ternary, not std::min: <winsock2.h> defines a `min`

// macro that would mangle std::min on the (compiled-but-discarded)

// Windows branch of this if constexpr.

constexpr int kDnsTimeoutMs = 2500;

int dnsTimeout = (timeoutMs > 0 && timeoutMs < kDnsTimeoutMs)

? timeoutMs : kDnsTimeoutMs;

for (const auto& ip : platform::resolve_fallback(host, dnsTimeout)) {

if (try_resolved(ip.c_str(), /*numeric=*/true)) return true;

}

return false;

};

// No libc resolver config but a relocatable one exists → resolve

// manually first to avoid a multi-second stall on a dead 127.0.0.1:53.

if (!platform::system_resolver_configured()) {

return try_manual() || try_resolved(host, /*numeric=*/false);

}

return try_resolved(host, /*numeric=*/false) || try_manual();

}

for (auto* rp = result; rp != nullptr; rp = rp->ai_next) {

SocketHandle fd = ::socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);

if (fd == INVALID_SOCKET_FD) {

continue;

}

// macOS and the BSDs spell "do not raise a signal" as a socket

// option rather than as a send flag; `write` below carries the flag

// for the platforms that have one.

//

// ⭐ NOTHING SELECTS THIS AND NOTHING MAY. It is not a feature, not

// a config field and not a runtime probe: the preprocessor reads the

// target's own <sys/socket.h> and the answer is already complete.

// Measured on this machine — glibc: SO_NOSIGPIPE absent,

// MSG_NOSIGNAL 0x4000; musl (Termux, Alpine, openkal-musl):

// SO_NOSIGPIPE absent, MSG_NOSIGNAL 0x4000; Darwin/BSD: the reverse;

// Windows: neither, and no SIGPIPE to raise.

//

// Making it selectable would be actively wrong. A consumer who left

// it off on macOS would get exactly issue #16 — the process killed

// by a signal it never armed — and would get it silently, on a

// platform they may not build for themselves. A property that only

// prevents harm and costs one setsockopt is not a choice worth

// offering; there is no target where the name exists and setting it

// is undesirable.

//

// This does NOT touch the process's signal disposition, so a program

// that wants SIGPIPE on its own stdout still gets it. That is the

// whole reason to prefer this over mbedtls's `signal(SIGPIPE,

// SIG_IGN)`, which changes it for everything the host does.

//

// Best-effort: a failure leaves the socket with the disposition it

// had before this line.

//

// #ifdef, not `if constexpr`: the name does not exist on Linux or

// Windows, and both arms of an `if constexpr` must compile.

#ifdef SO_NOSIGPIPE

int nosigpipe = 1;

::setsockopt(fd, SOL_SOCKET, SO_NOSIGPIPE,

reinterpret_cast<const char*>(&nosigpipe), sizeof(nosigpipe));

#endif

// Set non-blocking

if (!set_non_blocking(fd, true)) {

close_handle(fd);

continue;

}

int rc = ::connect(fd, rp->ai_addr, static_cast<int>(rp->ai_addrlen));

bool connected = false;

if (rc == 0) {

connected = true;

} else {

#ifdef _WIN32

if (WSAGetLastError() == WSAEWOULDBLOCK) {

#else

if (errno == EINPROGRESS) {

#endif

// Wait for connection with timeout

if (poll_fd(fd, timeoutMs, false)) {

int err = 0;

socklen_t len = sizeof(err);

if (::getsockopt(fd, SOL_SOCKET, SO_ERROR, reinterpret_cast<char*>(&err), &len) == 0 && err == 0) {

connected = true;

}

}

}

}

if (connected) {

// Restore blocking mode

set_non_blocking(fd, false);

fd_ = fd;

return true;

}

close_handle(fd);

}

return false;

}

int read(char* buf, int len) {

if (!is_valid()) return -1;

return static_cast<int>(::recv(fd_, buf, len, 0));

}

// A WRITE TO A SOCKET WHOSE PEER HAS GONE AWAY RAISES SIGPIPE, AND A

// PROGRAM THAT HAS NOT DISARMED IT — THE DEFAULT — IS KILLED RATHER THAN

// TOLD. That is issue #16, and it is this library's defect rather than its

// caller's: the fd is one this class created, and the write that meets a

// dead peer is most often the `close_notify` the pool's own clean-up sends.

//

// mbedtls guards against this in `net_prepare` (net_sockets.c:114) with a

// process-wide `signal(SIGPIPE, SIG_IGN)`. This library replaces mbedtls's

// network layer with its own BIO and never calls `mbedtls_net_init`, so it

// dropped that guard without putting anything in its place. MSG_NOSIGNAL is

// the better replacement in any case: a library has no business changing

// its host's signal disposition.

//

// The failure travels along paths that already exist — `bio_send` maps a

// non-positive return to MBEDTLS_ERR_NET_SEND_FAILED, and `TlsSocket::close`

// already ignores what close_notify returns — so the successful path is

// unchanged byte for byte.

//

// #ifdef, not `if constexpr`: the macro does not exist on Windows (which has

// no SIGPIPE either) or on the BSDs (which use SO_NOSIGPIPE, set in

// `connect_addrinfo`), and both arms of an `if constexpr` must compile. That

// is the trap 5e7d66f fixed in the resolver stubs.

//

// Above openkal the flag is accepted and ignored — openkal has no signals at

// all (openkal-musl `port/src/okm_net.c:546-550`) — so this compiles and is

// correct there without a branch of its own.

int write(const char* buf, int len) {

if (!is_valid()) return -1;

#ifdef MSG_NOSIGNAL

return static_cast<int>(::send(fd_, buf, len, MSG_NOSIGNAL));

#else

return static_cast<int>(::send(fd_, buf, len, 0));

#endif

}

bool wait_readable(int timeoutMs) {

if (!is_valid()) return false;

return poll_fd(fd_, timeoutMs, true);

}

bool wait_writable(int timeoutMs) {

if (!is_valid()) return false;

return poll_fd(fd_, timeoutMs, false);

}

[[nodiscard]] SocketHandle native_handle() const {

return fd_;

}

void close() {

if (is_valid()) {

close_handle(fd_);

fd_ = INVALID_SOCKET_FD;

}

}

static void platform_init() {

#ifdef _WIN32

WSADATA wsaData;

WSAStartup(MAKEWORD(2, 2), &wsaData);

#endif

}

static void platform_cleanup() {

#ifdef _WIN32

WSACleanup();

#endif

}

SocketHandle fd_ = INVALID_SOCKET_FD;

static bool set_non_blocking(SocketHandle fd, bool nonBlocking) {

#ifdef _WIN32

u_long mode = nonBlocking ? 1 : 0;

return ioctlsocket(fd, FIONBIO, &mode) == 0;

#else

int flags = ::fcntl(fd, F_GETFL, 0);

if (flags == -1) return false;

if (nonBlocking) {

flags |= O_NONBLOCK;

} else {

flags &= ~O_NONBLOCK;

}

return ::fcntl(fd, F_SETFL, flags) == 0;

#endif

}

static bool poll_fd(SocketHandle fd, int timeoutMs, bool forRead) {

#ifdef _WIN32

WSAPOLLFD pfd{};

pfd.fd = fd;

pfd.events = forRead ? POLLIN : POLLOUT;

int ret = WSAPoll(&pfd, 1, timeoutMs);

return ret > 0 && (pfd.revents & (pfd.events | POLLERR | POLLHUP));

#else

struct pollfd pfd{};

pfd.fd = fd;

pfd.events = forRead ? POLLIN : POLLOUT;

int ret = ::poll(&pfd, 1, timeoutMs);

return ret > 0 && (pfd.revents & (pfd.events | POLLERR | POLLHUP));

#endif

}

static void close_handle(SocketHandle fd) {

#ifdef _WIN32

::closesocket(fd);

#else

::close(fd);

#endif

}