open62541/plugins/ua_network_tcp.c

/* This work is licensed under a Creative Commons CCZero 1.0 Universal License.
 * See http://creativecommons.org/publicdomain/zero/1.0/ for more information. */

/* Enable POSIX features */
#ifndef _XOPEN_SOURCE
# define _XOPEN_SOURCE 600
#endif
#ifndef _DEFAULT_SOURCE
# define _DEFAULT_SOURCE
#endif
/* On older systems we need to define _BSD_SOURCE.
 * _DEFAULT_SOURCE is an alias for that. */
#ifndef _BSD_SOURCE
# define _BSD_SOURCE
#endif

/* Disable some security warnings on MSVC */
#ifdef _MSC_VER
# define _CRT_SECURE_NO_WARNINGS
#endif

/* Assume that Windows versions are newer than Windows XP */
#if defined(__MINGW32__) && (!defined(WINVER) || WINVER < 0x501)
# undef WINVER
# undef _WIN32_WINDOWS
# undef _WIN32_WINNT
# define WINVER 0x0501
# define _WIN32_WINDOWS 0x0501
# define _WIN32_WINNT 0x0501
#endif

#include "ua_network_tcp.h"
#include "ua_log_stdout.h"
#include "queue.h"

#include <stdio.h> // snprintf
#include <string.h> // memset
#include <errno.h>

#ifdef _WIN32
# include <winsock2.h>
# include <ws2tcpip.h>
# define CLOSESOCKET(S) closesocket((SOCKET)S)
# define ssize_t int
# define WIN32_INT (int)
# define OPTVAL_TYPE char
# define ERR_CONNECTION_PROGRESS WSAEWOULDBLOCK
# define UA_sleep_ms(X) Sleep(X)
#else
# define CLOSESOCKET(S) close(S)
# define SOCKET int
# define WIN32_INT
# define OPTVAL_TYPE int
# define ERR_CONNECTION_PROGRESS EINPROGRESS
# define UA_sleep_ms(X) usleep(X * 1000)
# include <arpa/inet.h>
# include <netinet/in.h>
# ifndef _WRS_KERNEL
#  include <sys/select.h>
# else
#  include <hostLib.h>
#  include <selectLib.h>
# endif
# include <sys/ioctl.h>
# include <fcntl.h>
# include <unistd.h> // read, write, close
# include <netdb.h>
# ifdef __QNX__
#  include <sys/socket.h>
# endif
#if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
# include <sys/param.h>
# if defined(BSD)
#  include<sys/socket.h>
# endif
#endif
# ifndef __CYGWIN__
#  include <netinet/tcp.h>
# endif
#endif

/* unsigned int for windows and workaround to a glibc bug */
/* Additionally if GNU_LIBRARY is not defined, it may be using
 * musl libc (e.g. Docker Alpine) */
#if defined(_WIN32) || defined(__OpenBSD__) || \
    (defined(__GNU_LIBRARY__) && (__GNU_LIBRARY__ <= 6) && \
     (__GLIBC__ <= 2) && (__GLIBC_MINOR__ < 16) || \
    !defined(__GNU_LIBRARY__))
# define UA_fd_set(fd, fds) FD_SET((unsigned int)fd, fds)
# define UA_fd_isset(fd, fds) FD_ISSET((unsigned int)fd, fds)
#else
# define UA_fd_set(fd, fds) FD_SET(fd, fds)
# define UA_fd_isset(fd, fds) FD_ISSET(fd, fds)
#endif

#ifdef UNDER_CE
# define errno WSAGetLastError()
#endif

#ifdef _WIN32
# define errno__ WSAGetLastError()
# define INTERRUPTED WSAEINTR
# define WOULDBLOCK WSAEWOULDBLOCK
# define AGAIN WSAEWOULDBLOCK
#else
# define errno__ errno
# define INTERRUPTED EINTR
# define WOULDBLOCK EWOULDBLOCK
# define AGAIN EAGAIN
#endif

/****************************/
/* Generic Socket Functions */
/****************************/

static UA_StatusCode
connection_getsendbuffer(UA_Connection *connection,
                         size_t length, UA_ByteString *buf) {
    if(length > connection->remoteConf.recvBufferSize)
        return UA_STATUSCODE_BADCOMMUNICATIONERROR;
    return UA_ByteString_allocBuffer(buf, length);
}

static void
connection_releasesendbuffer(UA_Connection *connection,
                             UA_ByteString *buf) {
    UA_ByteString_deleteMembers(buf);
}

static void
connection_releaserecvbuffer(UA_Connection *connection,
                             UA_ByteString *buf) {
    UA_ByteString_deleteMembers(buf);
}

static UA_StatusCode
connection_write(UA_Connection *connection, UA_ByteString *buf) {
    /* Prevent OS signals when sending to a closed socket */
    int flags = 0;
#ifdef MSG_NOSIGNAL
    flags |= MSG_NOSIGNAL;
#endif

    /* Send the full buffer. This may require several calls to send */
    size_t nWritten = 0;
    do {
        ssize_t n = 0;
        do {
            size_t bytes_to_send = buf->length - nWritten;
            n = send((SOCKET)connection->sockfd,
                     (const char*)buf->data + nWritten,
                     WIN32_INT bytes_to_send, flags);
            if(n < 0 && errno__ != INTERRUPTED && errno__ != AGAIN) {
                connection->close(connection);
                UA_ByteString_deleteMembers(buf);
                return UA_STATUSCODE_BADCONNECTIONCLOSED;
            }
        } while(n < 0);
        nWritten += (size_t)n;
    } while(nWritten < buf->length);

    /* Free the buffer */
    UA_ByteString_deleteMembers(buf);
    return UA_STATUSCODE_GOOD;
}

static UA_StatusCode
connection_recv(UA_Connection *connection, UA_ByteString *response,
                UA_UInt32 timeout) {
    response->data = (UA_Byte*)
        UA_malloc(connection->localConf.recvBufferSize);
    if(!response->data) {
        response->length = 0;
        return UA_STATUSCODE_BADOUTOFMEMORY; /* not enough memory retry */
    }

    /* Listen on the socket for the given timeout until a message arrives */
    if(timeout > 0) {
        fd_set fdset;
        FD_ZERO(&fdset);
        UA_fd_set(connection->sockfd, &fdset);
        UA_UInt32 timeout_usec = timeout * 1000;
        struct timeval tmptv = {(long int)(timeout_usec / 1000000),
                                (long int)(timeout_usec % 1000000)};
        int resultsize = select(connection->sockfd+1, &fdset, NULL,
                                NULL, &tmptv);

        /* No result */
        if(resultsize == 0)
            return UA_STATUSCODE_GOOD;
    }

    /* Get the received packet(s) */
    ssize_t ret = recv(connection->sockfd, (char*)response->data,
                       connection->localConf.recvBufferSize, 0);

    /* The remote side closed the connection */
    if(ret == 0) {
        UA_ByteString_deleteMembers(response);
        return UA_STATUSCODE_BADCONNECTIONCLOSED;
    }

    /* Error case */
    if(ret < 0) {
        UA_ByteString_deleteMembers(response);
        if(errno__ == INTERRUPTED || (timeout > 0) ?
           false : (errno__ == EAGAIN || errno__ == WOULDBLOCK))
            return UA_STATUSCODE_GOOD; /* statuscode_good but no data -> retry */
        connection->close(connection);
        return UA_STATUSCODE_BADCONNECTIONCLOSED;
    }

    /* Set the length of the received buffer */
    response->length = (size_t)ret;
    return UA_STATUSCODE_GOOD;
}

static UA_StatusCode
socket_set_nonblocking(SOCKET sockfd) {
#ifdef _WIN32
    u_long iMode = 1;
    if(ioctlsocket(sockfd, FIONBIO, &iMode) != NO_ERROR)
        return UA_STATUSCODE_BADINTERNALERROR;
#elif defined(_WRS_KERNEL)
    int on = TRUE;
    if(ioctl(sockfd, FIONBIO, &on) < 0)
      return UA_STATUSCODE_BADINTERNALERROR;
#else
    int opts = fcntl(sockfd, F_GETFL);
    if(opts < 0 || fcntl(sockfd, F_SETFL, opts|O_NONBLOCK) < 0)
        return UA_STATUSCODE_BADINTERNALERROR;
#endif
    return UA_STATUSCODE_GOOD;
}

static UA_StatusCode
socket_set_blocking(SOCKET sockfd) {
#ifdef _WIN32
    u_long iMode = 0;
    if(ioctlsocket(sockfd, FIONBIO, &iMode) != NO_ERROR)
        return UA_STATUSCODE_BADINTERNALERROR;
#else
    int opts = fcntl(sockfd, F_GETFL);
    if(opts < 0 || fcntl(sockfd, F_SETFL, opts & (~O_NONBLOCK)) < 0)
        return UA_STATUSCODE_BADINTERNALERROR;
#endif
    return UA_STATUSCODE_GOOD;
}

/***************************/
/* Server NetworkLayer TCP */
/***************************/

#define MAXBACKLOG 100

typedef struct ConnectionEntry {
    UA_Connection connection;
    LIST_ENTRY(ConnectionEntry) pointers;
} ConnectionEntry;

typedef struct {
    UA_ConnectionConfig conf;
    UA_UInt16 port;
    UA_Int32 serverSockets[FD_SETSIZE];
    UA_UInt16 serverSocketsSize;
    LIST_HEAD(, ConnectionEntry) connections;
} ServerNetworkLayerTCP;

static void
ServerNetworkLayerTCP_freeConnection(UA_Connection *connection) {
    UA_Connection_deleteMembers(connection);
    UA_free(connection);
}

/* This performs only 'shutdown'. 'close' is called when the shutdown
 * socket is returned from select. */
static void
ServerNetworkLayerTCP_close(UA_Connection *connection) {
    shutdown((SOCKET)connection->sockfd, 2);
    connection->state = UA_CONNECTION_CLOSED;
}

static UA_StatusCode
ServerNetworkLayerTCP_add(ServerNetworkLayerTCP *layer, UA_Int32 newsockfd,
                          struct sockaddr_storage *remote) {
    /* Set nonblocking */
    socket_set_nonblocking(newsockfd);

    /* Do not merge packets on the socket (disable Nagle's algorithm) */
    int dummy = 1;
    if(setsockopt(newsockfd, IPPROTO_TCP, TCP_NODELAY,
               (const char *)&dummy, sizeof(dummy)) < 0) {
        UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                     "Cannot set socket option TCP_NODELAY. Error: %s",
                     strerror(errno));
        return UA_STATUSCODE_BADUNEXPECTEDERROR;
    }

    /* Get the peer name for logging */
    char remote_name[100];
    int res = getnameinfo((struct sockaddr*)remote,
                          sizeof(struct sockaddr_storage),
                          remote_name, sizeof(remote_name),
                          NULL, 0, NI_NUMERICHOST);
    if(res == 0) {
        UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                    "Connection %i | New connection over TCP from %s",
                    (int)newsockfd, remote_name);
    } else {
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "Connection %i | New connection over TCP, "
                       "getnameinfo failed with errno %i",
                       (int)newsockfd, errno__);
    }

    /* Allocate and initialize the connection */
    ConnectionEntry *e = (ConnectionEntry*)UA_malloc(sizeof(ConnectionEntry));
    if(!e)
        return UA_STATUSCODE_BADOUTOFMEMORY;

    UA_Connection *c = &e->connection;
    memset(c, 0, sizeof(UA_Connection));
    c->sockfd = newsockfd;
    c->handle = layer;
    c->localConf = layer->conf;
    c->remoteConf = layer->conf;
    c->send = connection_write;
    c->close = ServerNetworkLayerTCP_close;
    c->free = ServerNetworkLayerTCP_freeConnection;
    c->getSendBuffer = connection_getsendbuffer;
    c->releaseSendBuffer = connection_releasesendbuffer;
    c->releaseRecvBuffer = connection_releaserecvbuffer;
    c->state = UA_CONNECTION_OPENING;

    /* Add to the linked list */
    LIST_INSERT_HEAD(&layer->connections, e, pointers);
    return UA_STATUSCODE_GOOD;
}

static void
addServerSocket(ServerNetworkLayerTCP *layer, struct addrinfo *ai) {
    /* Create the server socket */
    SOCKET newsock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
#ifdef _WIN32
    if(newsock == INVALID_SOCKET)
#else
    if(newsock < 0)
#endif
    {
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "Error opening the server socket");
        return;
    }

    /* Some Linux distributions have net.ipv6.bindv6only not activated. So
     * sockets can double-bind to IPv4 and IPv6. This leads to problems. Use
     * AF_INET6 sockets only for IPv6. */
    int optval = 1;
    if(ai->ai_family == AF_INET6 &&
       setsockopt(newsock, IPPROTO_IPV6, IPV6_V6ONLY,
                  (const char*)&optval, sizeof(optval)) == -1) {
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "Could not set an IPv6 socket to IPv6 only");
        CLOSESOCKET(newsock);
        return;
    }

    if(setsockopt(newsock, SOL_SOCKET, SO_REUSEADDR,
                  (const char *)&optval, sizeof(optval)) == -1) {
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "Could not make the socket reusable");
        CLOSESOCKET(newsock);
        return;
    }

    if(socket_set_nonblocking(newsock) != UA_STATUSCODE_GOOD) {
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "Could not set the server socket to nonblocking");
        CLOSESOCKET(newsock);
        return;
    }

    /* Bind socket to address */
    if(bind(newsock, ai->ai_addr, WIN32_INT ai->ai_addrlen) < 0) {
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "Error binding a server socket: %i", errno__);
        CLOSESOCKET(newsock);
        return;
    }

    /* Start listening */
    if(listen(newsock, MAXBACKLOG) < 0) {
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "Error listening on server socket");
        CLOSESOCKET(newsock);
        return;
    }

    layer->serverSockets[layer->serverSocketsSize] = (UA_Int32)newsock;
    layer->serverSocketsSize++;
}

static UA_StatusCode
ServerNetworkLayerTCP_start(UA_ServerNetworkLayer *nl) {
#ifdef _WIN32
    WORD wVersionRequested = MAKEWORD(2, 2);
    WSADATA wsaData;
    WSAStartup(wVersionRequested, &wsaData);
#endif

    ServerNetworkLayerTCP *layer = (ServerNetworkLayerTCP *)nl->handle;

    /* Get the discovery url from the hostname */
    UA_String du = UA_STRING_NULL;
    char hostname[256];
    if(gethostname(hostname, 255) == 0) {
        char discoveryUrl[256];
#ifndef _MSC_VER
        du.length = (size_t)snprintf(discoveryUrl, 255, "opc.tcp://%s:%d/",
                                     hostname, layer->port);
#else
        du.length = (size_t)_snprintf_s(discoveryUrl, 255, _TRUNCATE,
                                        "opc.tcp://%s:%d/", hostname,
                    layer->port);
#endif
        du.data = (UA_Byte*)discoveryUrl;
    }
    UA_String_copy(&du, &nl->discoveryUrl);

    /* Get addrinfo of the server and create server sockets */
    char portno[6];
#ifndef _MSC_VER
    snprintf(portno, 6, "%d", layer->port);
#else
    _snprintf_s(portno, 6, _TRUNCATE, "%d", layer->port);
#endif
    struct addrinfo hints, *res;
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;
    if(getaddrinfo(NULL, portno, &hints, &res) != 0)
        return UA_STATUSCODE_BADINTERNALERROR;

    /* There might be serveral addrinfos (for different network cards,
     * IPv4/IPv6). Add a server socket for all of them. */
    struct addrinfo *ai = res;
    for(layer->serverSocketsSize = 0;
        layer->serverSocketsSize < FD_SETSIZE && ai != NULL;
        ai = ai->ai_next)
        addServerSocket(layer, ai);
    freeaddrinfo(res);

    UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                "TCP network layer listening on %.*s",
                (int)nl->discoveryUrl.length, nl->discoveryUrl.data);
    return UA_STATUSCODE_GOOD;
}

/* After every select, reset the sockets to listen on */
static UA_Int32
setFDSet(ServerNetworkLayerTCP *layer, fd_set *fdset) {
    FD_ZERO(fdset);
    UA_Int32 highestfd = 0;
    for(UA_UInt16 i = 0; i < layer->serverSocketsSize; i++) {
        UA_fd_set(layer->serverSockets[i], fdset);
        if(layer->serverSockets[i] > highestfd)
            highestfd = layer->serverSockets[i];
    }

    ConnectionEntry *e;
    LIST_FOREACH(e, &layer->connections, pointers) {
        UA_fd_set(e->connection.sockfd, fdset);
        if(e->connection.sockfd > highestfd)
            highestfd = e->connection.sockfd;
    }

    return highestfd;
}

static UA_StatusCode
ServerNetworkLayerTCP_listen(UA_ServerNetworkLayer *nl, UA_Server *server,
                             UA_UInt16 timeout) {
    /* Every open socket can generate two jobs */
    ServerNetworkLayerTCP *layer = (ServerNetworkLayerTCP *)nl->handle;

    /* Listen on open sockets (including the server) */
    fd_set fdset, errset;
    UA_Int32 highestfd = setFDSet(layer, &fdset);
    setFDSet(layer, &errset);
    struct timeval tmptv = {0, timeout * 1000};
    if (select(highestfd+1, &fdset, NULL, &errset, &tmptv) < 0) {
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "Socket select failed with %s", strerror(errno));
    }

    /* Accept new connections via the server sockets */
    for(UA_UInt16 i = 0; i < layer->serverSocketsSize; i++) {
        if(!UA_fd_isset(layer->serverSockets[i], &fdset))
            continue;

        struct sockaddr_storage remote;
        socklen_t remote_size = sizeof(remote);
        SOCKET newsockfd = accept((SOCKET)layer->serverSockets[i],
                                  (struct sockaddr*)&remote, &remote_size);
#ifdef _WIN32
        if(newsockfd == INVALID_SOCKET)
#else
        if(newsockfd < 0)
#endif
            continue;

        UA_LOG_TRACE(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                    "Connection %i | New TCP connection on server socket %i",
                    (int)newsockfd, layer->serverSockets[i]);

        ServerNetworkLayerTCP_add(layer, (UA_Int32)newsockfd, &remote);
    }

    /* Read from established sockets */
    ConnectionEntry *e, *e_tmp;
    LIST_FOREACH_SAFE(e, &layer->connections, pointers, e_tmp) {
        if(!UA_fd_isset(e->connection.sockfd, &errset) &&
           !UA_fd_isset(e->connection.sockfd, &fdset))
          continue;

        UA_LOG_TRACE(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                    "Connection %i | Activity on the socket",
                    e->connection.sockfd);

        UA_ByteString buf = UA_BYTESTRING_NULL;
        UA_StatusCode retval = connection_recv(&e->connection, &buf, 0);

        if(retval == UA_STATUSCODE_GOOD) {
            /* Process packets */
            UA_Server_processBinaryMessage(server, &e->connection, &buf);
            connection_releaserecvbuffer(&e->connection, &buf);
        } else if(retval == UA_STATUSCODE_BADCONNECTIONCLOSED) {
            /* The socket is shutdown but not closed */
            if(e->connection.state != UA_CONNECTION_CLOSED) {
                UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                            "Connection %i | Closed by the client",
                            e->connection.sockfd);
            } else {
                UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                            "Connection %i | Closed by the server",
                            e->connection.sockfd);
            }
            LIST_REMOVE(e, pointers);
            CLOSESOCKET(e->connection.sockfd);
            UA_Server_removeConnection(server, &e->connection);
        }
    }
    return UA_STATUSCODE_GOOD;
}

static void
ServerNetworkLayerTCP_stop(UA_ServerNetworkLayer *nl, UA_Server *server) {
    ServerNetworkLayerTCP *layer = (ServerNetworkLayerTCP *)nl->handle;
    UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                "Shutting down the TCP network layer");

    /* Close the server sockets */
    for(UA_UInt16 i = 0; i < layer->serverSocketsSize; i++) {
        shutdown((SOCKET)layer->serverSockets[i], 2);
        CLOSESOCKET(layer->serverSockets[i]);
    }
    layer->serverSocketsSize = 0;

    /* Close open connections */
    ConnectionEntry *e;
    LIST_FOREACH(e, &layer->connections, pointers)
        ServerNetworkLayerTCP_close(&e->connection);

    /* Run recv on client sockets. This picks up the closed sockets and frees
     * the connection. */
    ServerNetworkLayerTCP_listen(nl, server, 0);

#ifdef _WIN32
    WSACleanup();
#endif
}

/* run only when the server is stopped */
static void
ServerNetworkLayerTCP_deleteMembers(UA_ServerNetworkLayer *nl) {
    ServerNetworkLayerTCP *layer = (ServerNetworkLayerTCP *)nl->handle;
    UA_String_deleteMembers(&nl->discoveryUrl);

    /* Hard-close and remove remaining connections. The server is no longer
     * running. So this is safe. */
    ConnectionEntry *e, *e_tmp;
    LIST_FOREACH_SAFE(e, &layer->connections, pointers, e_tmp) {
        LIST_REMOVE(e, pointers);
        ServerNetworkLayerTCP_close(&e->connection);
        CLOSESOCKET(e->connection.sockfd);
        UA_free(e);
    }

    /* Free the layer */
    UA_free(layer);
}

UA_ServerNetworkLayer
UA_ServerNetworkLayerTCP(UA_ConnectionConfig conf, UA_UInt16 port) {
    UA_ServerNetworkLayer nl;
    memset(&nl, 0, sizeof(UA_ServerNetworkLayer));
    ServerNetworkLayerTCP *layer = (ServerNetworkLayerTCP*)
        UA_calloc(1,sizeof(ServerNetworkLayerTCP));
    if(!layer)
        return nl;

    layer->conf = conf;
    layer->port = port;

    nl.handle = layer;
    nl.start = ServerNetworkLayerTCP_start;
    nl.listen = ServerNetworkLayerTCP_listen;
    nl.stop = ServerNetworkLayerTCP_stop;
    nl.deleteMembers = ServerNetworkLayerTCP_deleteMembers;
    return nl;
}

/***************************/
/* Client NetworkLayer TCP */
/***************************/

static void
ClientNetworkLayerTCP_close(UA_Connection *connection) {
    shutdown((SOCKET)connection->sockfd, 2);
    CLOSESOCKET(connection->sockfd);
    connection->state = UA_CONNECTION_CLOSED;
}

UA_Connection
UA_ClientConnectionTCP(UA_ConnectionConfig conf,
                       const char *endpointUrl, const UA_UInt32 timeout) {
#ifdef _WIN32
    WORD wVersionRequested;
    WSADATA wsaData;
    wVersionRequested = MAKEWORD(2, 2);
    WSAStartup(wVersionRequested, &wsaData);
#endif

    UA_Connection connection;
    memset(&connection, 0, sizeof(UA_Connection));
    connection.state = UA_CONNECTION_OPENING;
    connection.localConf = conf;
    connection.remoteConf = conf;
    connection.send = connection_write;
    connection.recv = connection_recv;
    connection.close = ClientNetworkLayerTCP_close;
    connection.free = NULL;
    connection.getSendBuffer = connection_getsendbuffer;
    connection.releaseSendBuffer = connection_releasesendbuffer;
    connection.releaseRecvBuffer = connection_releaserecvbuffer;

    UA_String endpointUrlString = UA_STRING((char*)(uintptr_t)endpointUrl);
    UA_String hostnameString = UA_STRING_NULL;
    UA_String pathString = UA_STRING_NULL;
    UA_UInt16 port = 0;
    char hostname[512];

    UA_StatusCode parse_retval =
        UA_parseEndpointUrl(&endpointUrlString, &hostnameString,
                            &port, &pathString);
    if(parse_retval != UA_STATUSCODE_GOOD || hostnameString.length > 511) {
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "Server url is invalid: %s", endpointUrl);
        return connection;
    }
    memcpy(hostname, hostnameString.data, hostnameString.length);
    hostname[hostnameString.length] = 0;

    if(port == 0) {
        port = 4840;
        UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                    "No port defined, using default port %d", port);
    }

    struct addrinfo hints, *server;
    memset(&hints, 0, sizeof(hints));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    char portStr[6];
#ifndef _MSC_VER
    snprintf(portStr, 6, "%d", port);
#else
    _snprintf_s(portStr, 6, _TRUNCATE, "%d", port);
#endif
    int error = getaddrinfo(hostname, portStr, &hints, &server);
    if(error != 0 || !server) {
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "DNS lookup of %s failed with error %s",
                       hostname, gai_strerror(error));
        return connection;
    }


    UA_Boolean connected = UA_FALSE;

    UA_DateTime connStart = UA_DateTime_nowMonotonic();
    SOCKET clientsockfd;

    /* On linux connect may immediately return with ECONNREFUSED but we still
     * want to try to connect. So use a loop and retry until timeout is
     * reached. */
    do {
        /* Get a socket */
        clientsockfd = socket(server->ai_family,
                              server->ai_socktype,
                              server->ai_protocol);
    #ifdef _WIN32
        if(clientsockfd == INVALID_SOCKET) {
    #else
        if(clientsockfd < 0) {
    #endif
            UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                           "Could not create client socket: %s", strerror(errno__));
            freeaddrinfo(server);
            return connection;
        }

        /* Connect to the server */
        connection.sockfd = (UA_Int32) clientsockfd; /* cast for win32 */

        /* Non blocking connect to be able to timeout */
        if (socket_set_nonblocking(clientsockfd) != UA_STATUSCODE_GOOD) {
            UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                           "Could not set the client socket to nonblocking");
            ClientNetworkLayerTCP_close(&connection);
            freeaddrinfo(server);
            return connection;
        }

        /* Non blocking connect */
        error = connect(clientsockfd, server->ai_addr,
                        WIN32_INT server->ai_addrlen);

        if ((error == -1) && (errno__ != ERR_CONNECTION_PROGRESS)) {
            ClientNetworkLayerTCP_close(&connection);
            UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                           "Connection to %s failed with error: %s",
                           endpointUrl, strerror(errno__));
            freeaddrinfo(server);
            return connection;
        }

        /* Use select to wait and check if connected */
        if (error == -1 && (errno__ == ERR_CONNECTION_PROGRESS)) {
            /* connection in progress. Wait until connected using select */
            UA_UInt32 timeSinceStart = (UA_UInt32)
                ((UA_Double)(UA_DateTime_nowMonotonic() - connStart) * UA_DATETIME_TO_MSEC);
            if(timeSinceStart > timeout)
                break;

            fd_set fdset;
            FD_ZERO(&fdset);
            UA_fd_set(clientsockfd, &fdset);
            UA_UInt32 timeout_usec = (timeout - timeSinceStart) * 1000;
            struct timeval tmptv = {(long int) (timeout_usec / 1000000),
                                    (long int) (timeout_usec % 1000000)};

            int resultsize = select((UA_Int32)(clientsockfd + 1), NULL, &fdset,
                                    NULL, &tmptv);

            if (resultsize == 1) {
                /* Windows does not have any getsockopt equivalent and it is not
                 * needed there */
#ifdef _WIN32
                connected = true;
                break;
#else
                OPTVAL_TYPE so_error;
                socklen_t len = sizeof so_error;

                int ret = getsockopt(clientsockfd, SOL_SOCKET, SO_ERROR, &so_error, &len);

                if (ret != 0 || so_error != 0) {
                    /* on connection refused we should still try to connect */
                    /* connection refused happens on localhost or local ip without timeout */
                    if (so_error != ECONNREFUSED) {
                        ClientNetworkLayerTCP_close(&connection);
                        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                                       "Connection to %s failed with error: %s",
                                       endpointUrl, strerror(ret == 0 ? so_error : errno__));
                        freeaddrinfo(server);
                        return connection;
                    }
                    /* wait until we try a again. Do not make this too small, otherwise the
                     * timeout is somehow wrong */
                    UA_sleep_ms(100);
                } else {
                    connected = true;
                    break;
                }
#endif
            }
        } else {
            connected = true;
            break;
        }
        ClientNetworkLayerTCP_close(&connection);

    } while ((UA_Double)(UA_DateTime_nowMonotonic() - connStart)*UA_DATETIME_TO_MSEC < timeout);

    freeaddrinfo(server);
    if (!connected) {
        /* connection timeout */
        ClientNetworkLayerTCP_close(&connection);
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "Trying to connect to %s timed out",
                       endpointUrl);
        return connection;
    }


    /* We are connected. Reset socket to blocking */
    if(socket_set_blocking(clientsockfd) != UA_STATUSCODE_GOOD) {
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "Could not set the client socket to blocking");
        ClientNetworkLayerTCP_close(&connection);
        return connection;
    }

#ifdef SO_NOSIGPIPE
    int val = 1;
    int sso_result = setsockopt(connection.sockfd, SOL_SOCKET,
                                SO_NOSIGPIPE, (void*)&val, sizeof(val));
    if(sso_result < 0)
        UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_NETWORK,
                       "Couldn't set SO_NOSIGPIPE");
#endif

    return connection;
}