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. */

#if defined(__MINGW32__) && (!defined(WINVER) || WINVER < 0x501)
/* Assume the target is newer than Windows XP */
# 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 "queue.h"

#include <stdlib.h> // malloc, free
#include <stdio.h> // snprintf
#include <string.h> // memset
#include <errno.h>
#if UNDER_CE
#define errno WSAGetLastError()
#endif
#ifdef _WIN32
# ifndef __clang__
#  include <malloc.h>
# endif
/* inet_ntoa is deprecated on MSVC but used for compatibility */
# define _WINSOCK_DEPRECATED_NO_WARNINGS
# include <winsock2.h>
# include <ws2tcpip.h>
# define CLOSESOCKET(S) closesocket((SOCKET)S)
# define ssize_t int
# define WIN32_INT (int)
#else
# define CLOSESOCKET(S) close(S)
# define SOCKET int
# define WIN32_INT
# include <arpa/inet.h>
# include <netinet/in.h>
# include <sys/select.h>
# 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 UA_ENABLE_MULTITHREADING
# include <urcu/uatomic.h>
#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 void
socket_close(UA_Connection *connection) {
    connection->state = UA_CONNECTION_CLOSED;
    shutdown((SOCKET)connection->sockfd,2);
    CLOSESOCKET(connection->sockfd);
}

static UA_StatusCode
socket_write(UA_Connection *connection, UA_ByteString *buf) {
    size_t nWritten = 0;
    do {
        ssize_t n = 0;
        do {
        /* If the OS throws EMSGSIZE, force a smaller packet size:
         * size_t bytes_to_send = buf->length - nWritten >  1024 ? 1024 : buf->length - nWritten; */
            size_t bytes_to_send = buf->length - nWritten;
            n = send((SOCKET)connection->sockfd, (const char*)buf->data + nWritten,
                     WIN32_INT bytes_to_send, 0);
            if(n < 0 && errno__ != INTERRUPTED && errno__ != AGAIN) {
                connection->close(connection);
                socket_close(connection);
                UA_ByteString_deleteMembers(buf);
                return UA_STATUSCODE_BADCONNECTIONCLOSED;
            }
        } while(n < 0);
        nWritten += (size_t)n;
    } while(nWritten < buf->length);
    UA_ByteString_deleteMembers(buf);
    return UA_STATUSCODE_GOOD;
}

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

    if(timeout > 0) {
        /* currently, only the client uses timeouts */
#ifndef _WIN32
        UA_UInt32 timeout_usec = timeout * 1000;
# ifdef __APPLE__
        struct timeval tmptv = {(long int)(timeout_usec / 1000000), timeout_usec % 1000000};
# else
        struct timeval tmptv = {(long int)(timeout_usec / 1000000), (long int)(timeout_usec % 1000000)};
# endif
        int ret = setsockopt(connection->sockfd, SOL_SOCKET, SO_RCVTIMEO,
                             (const char *)&tmptv, sizeof(struct timeval));
#else
        DWORD timeout_dw = timeout;
        int ret = setsockopt(connection->sockfd, SOL_SOCKET, SO_RCVTIMEO,
                             (const char*)&timeout_dw, sizeof(DWORD));
#endif
        if(0 != ret) {
            UA_ByteString_deleteMembers(response);
            socket_close(connection);
            return UA_STATUSCODE_BADCONNECTIONCLOSED;
        }
    }

#ifdef __CYGWIN__
    /* Workaround for https://cygwin.com/ml/cygwin/2013-07/msg00107.html */
    ssize_t ret;
    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 retval = select(connection->sockfd+1, &fdset, NULL, NULL, &tmptv);
        if(retval && UA_fd_isset(connection->sockfd, &fdset)) {
            ret = recv(connection->sockfd, (char*)response->data,
                       connection->localConf.recvBufferSize, 0);
        } else {
            ret = 0;
        }
    } else {
        ret = recv(connection->sockfd, (char*)response->data,
                   connection->localConf.recvBufferSize, 0);
    }
#else
    ssize_t ret = recv(connection->sockfd, (char*)response->data,
                       connection->localConf.recvBufferSize, 0);
#endif

    /* server has closed the connection */
    if(ret == 0) {
        UA_ByteString_deleteMembers(response);
        socket_close(connection);
        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 */
        socket_close(connection);
        return UA_STATUSCODE_BADCONNECTIONCLOSED;
    }
    
    /* default case */
    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;
#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 */
/***************************/

/**
 * For the multithreaded mode, assume a single thread that periodically "gets
 * work" from the network layer. In addition, several worker threads are
 * asynchronously calling into the callbacks of the UA_Connection that holds a
 * single connection.
 *
 * Creating a connection: When "GetJobs" encounters a new connection, it creates
 * a UA_Connection with the socket information. This is added to the mappings
 * array that links sockets to UA_Connection structs.
 *
 * Reading data: In "GetJobs", we listen on the sockets in the mappings array.
 * If data arrives (or the connection closes), a WorkItem is created that
 * carries the work and a pointer to the connection.
 *
 * Closing a connection: Closing can happen in two ways. Either it is triggered
 * by the server in an asynchronous callback. Or the connection is close by the
 * client and this is detected in "GetJobs". The server needs to do some
 * internal cleanups (close attached securechannels, etc.). So even when a
 * closed connection is detected in "GetJobs", we trigger the server to close
 * the connection (with a WorkItem) and continue from the callback.
 *
 * - Server calls close-callback: We close the socket, set the connection-state
 *   to closed and add the connection to a linked list from which it is deleted
 *   later. The connection cannot be freed right away since other threads might
 *   still be using it.
 *
 * - GetJobs: We remove the connection from the mappings array. In the
 *   non-multithreaded case, the connection is freed. For multithreading, we
 *   return a workitem that is delayed, i.e. that is called only after all
 *   workitems created before are finished in all threads. This workitems
 *   contains a callback that goes through the linked list of connections to be
 *   freed. */

#define MAXBACKLOG 100

/* UA_Connection is the first element. We can exchange pointers to the first
 * element and free the entire structure. */
typedef struct ConnectionEntry {
    UA_Connection connection;
    LIST_ENTRY(ConnectionEntry) pointers;
} ConnectionEntry;

typedef struct {
    UA_ConnectionConfig conf;
    UA_UInt16 port;
    UA_Logger logger; // Set during start

    /* open sockets and connections */
    UA_Int32 serversockfd;
    LIST_HEAD(, ConnectionEntry) connections;
} ServerNetworkLayerTCP;

static UA_StatusCode
ServerNetworkLayerGetSendBuffer(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
ServerNetworkLayerReleaseSendBuffer(UA_Connection *connection,
                                    UA_ByteString *buf) {
    UA_ByteString_deleteMembers(buf);
}

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

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

/* Callback triggered from the server (any thread). Only "shutdown" here. This
 * triggers the select, where the connection is closed and freed in the server's
 * mainloop. */
static void
ServerNetworkLayerTCP_closeConnection(UA_Connection *connection) {
    connection->state = UA_CONNECTION_CLOSED;
    UA_LOG_INFO(((ServerNetworkLayerTCP*)connection->handle)->logger,
                UA_LOGCATEGORY_NETWORK,
                "Connection %i | Force closing the connection",
                connection->sockfd);
    shutdown(connection->sockfd, 2);
}

static UA_StatusCode
ServerNetworkLayerTCP_add(ServerNetworkLayerTCP *layer, UA_Int32 newsockfd) {
    /* Look up the peer name for logging */
    struct sockaddr_in addr;
    socklen_t addrlen = sizeof(struct sockaddr_in);
    int res = getpeername(newsockfd, (struct sockaddr*)&addr, &addrlen);
    if(res == 0) {
        UA_LOG_INFO(layer->logger, UA_LOGCATEGORY_NETWORK,
                    "Connection %i | New connection over TCP from %s:%d",
                    newsockfd, inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));
    } else {
        UA_LOG_WARNING(layer->logger, UA_LOGCATEGORY_NETWORK,
                       "Connection %i | New connection over TCP, "
                       "getpeername failed with errno %i", newsockfd, errno);
    }

    /* Allocate and initialize the connection */
    ConnectionEntry *e = (ConnectionEntry*)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 = socket_write;
    c->close = ServerNetworkLayerTCP_closeConnection;
    c->free = ServerNetworkLayerTCP_freeConnection;
    c->getSendBuffer = ServerNetworkLayerGetSendBuffer;
    c->releaseSendBuffer = ServerNetworkLayerReleaseSendBuffer;
    c->releaseRecvBuffer = ServerNetworkLayerReleaseRecvBuffer;
    c->state = UA_CONNECTION_OPENING;

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

static UA_StatusCode
ServerNetworkLayerTCP_start(UA_ServerNetworkLayer *nl, UA_Logger logger) {
    ServerNetworkLayerTCP *layer = (ServerNetworkLayerTCP *)nl->handle;
    layer->logger = logger;

    /* 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);

    /* Create the server socket */
    SOCKET newsock = socket(AF_INET6, SOCK_STREAM, 0);
#ifdef _WIN32
    if(newsock == INVALID_SOCKET)
#else
    if(newsock < 0)
#endif
    {
        UA_LOG_WARNING(layer->logger, UA_LOGCATEGORY_NETWORK,
                       "Error opening the server socket");
        return UA_STATUSCODE_BADINTERNALERROR;
    }

    /* Set socket options */
    int optval = 1;
    if(setsockopt(newsock, SOL_SOCKET, SO_REUSEADDR,
                  (const char *)&optval, sizeof(optval)) == -1 ||
       socket_set_nonblocking(newsock) != UA_STATUSCODE_GOOD) {
        UA_LOG_WARNING(layer->logger, UA_LOGCATEGORY_NETWORK,
                       "Error during setting of server socket options");
        CLOSESOCKET(newsock);
        return UA_STATUSCODE_BADINTERNALERROR;
    }

    /* Bind socket to address */
    struct sockaddr_in6 serv_addr;
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin6_family = AF_INET6;
    serv_addr.sin6_port = htons(layer->port);
    serv_addr.sin6_addr = in6addr_any;
    if(bind(newsock, (const struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
        UA_LOG_WARNING(layer->logger, UA_LOGCATEGORY_NETWORK,
                       "Error during binding of the server socket");
        CLOSESOCKET(newsock);
        return UA_STATUSCODE_BADINTERNALERROR;
    }

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

    layer->serversockfd = (UA_Int32)newsock; /* cast on win32 */
    UA_LOG_INFO(layer->logger, UA_LOGCATEGORY_NETWORK,
                "TCP network layer listening on %.*s",
                nl->discoveryUrl.length, nl->discoveryUrl.data);
    return UA_STATUSCODE_GOOD;
}

/* Remove closed connections before going into "listen". Returns whether a
 * connection was removed. */
static void
removeClosedConnections(ServerNetworkLayerTCP *layer, UA_Server *server) {
    ConnectionEntry *e, *e_tmp;
    LIST_FOREACH_SAFE(e, &layer->connections, pointers, e_tmp) {
        if(e->connection.state != UA_CONNECTION_CLOSED)
            continue;
        LIST_REMOVE(e, pointers);
        UA_Server_removeConnection(server, &e->connection);
    }
}

/* After every select, we need to reset the sockets we want to listen on */
static UA_Int32
setFDSet(ServerNetworkLayerTCP *layer, fd_set *fdset) {
    FD_ZERO(fdset);
    UA_fd_set(layer->serversockfd, fdset);
    UA_Int32 highestfd = layer->serversockfd;
    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;

    /* Remove closed sockets */
    removeClosedConnections(layer, server);

    /* 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};
    UA_Int32 resultsize = select(highestfd+1, &fdset, NULL, &errset, &tmptv);

    /* Accept new connection via the server socket (can only be a single one) */
    if(UA_fd_isset(layer->serversockfd, &fdset)) {
        --resultsize;
        SOCKET newsockfd = accept((SOCKET)layer->serversockfd, NULL, NULL);
#ifdef _WIN32
        if(newsockfd != INVALID_SOCKET)
#else
        if(newsockfd >= 0)
#endif
        {
            socket_set_nonblocking(newsockfd);
            /* Do not merge packets on the socket (disable Nagle's algorithm) */
            int i = 1;
            setsockopt(newsockfd, IPPROTO_TCP, TCP_NODELAY, (const char *)&i, sizeof(i));
            ServerNetworkLayerTCP_add(layer, (UA_Int32)newsockfd);
        }
    }

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

        UA_StatusCode retval = socket_recv(&e->connection, &buf, 0);
        if(retval == UA_STATUSCODE_GOOD) {
            UA_Server_processBinaryMessage(server, &e->connection, &buf);
        } else if (retval == UA_STATUSCODE_BADCONNECTIONCLOSED) {
            LIST_REMOVE(e, pointers);
            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(layer->logger, UA_LOGCATEGORY_NETWORK,
                "Shutting down the TCP network layer");
    shutdown((SOCKET)layer->serversockfd,2);
    CLOSESOCKET(layer->serversockfd);
    ConnectionEntry *e, *e_tmp;
    LIST_FOREACH_SAFE(e, &layer->connections, pointers, e_tmp) {
        LIST_REMOVE(e, pointers);
        UA_Server_removeConnection(server, &e->connection);
    }
#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);
    UA_free(layer);
}

UA_ServerNetworkLayer
UA_ServerNetworkLayerTCP(UA_ConnectionConfig conf, UA_UInt16 port) {
#ifdef _WIN32
    WORD wVersionRequested;
    WSADATA wsaData;
    wVersionRequested = MAKEWORD(2, 2);
    WSAStartup(wVersionRequested, &wsaData);
#endif

    UA_ServerNetworkLayer nl;
    memset(&nl, 0, sizeof(UA_ServerNetworkLayer));
    ServerNetworkLayerTCP *layer = (ServerNetworkLayerTCP *)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 UA_StatusCode
ClientNetworkLayerGetBuffer(UA_Connection *connection, size_t length,
                            UA_ByteString *buf) {
    if(length > connection->remoteConf.recvBufferSize)
        return UA_STATUSCODE_BADCOMMUNICATIONERROR;
    if(connection->state == UA_CONNECTION_CLOSED)
        return UA_STATUSCODE_BADCONNECTIONCLOSED;
    return UA_ByteString_allocBuffer(buf, connection->remoteConf.recvBufferSize);
}

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

static void
ClientNetworkLayerClose(UA_Connection *connection) {
#ifdef UA_ENABLE_MULTITHREADING
    if(uatomic_xchg(&connection->state, UA_CONNECTION_CLOSED) == UA_CONNECTION_CLOSED)
        return;
#else
    if(connection->state == UA_CONNECTION_CLOSED)
        return;
    connection->state = UA_CONNECTION_CLOSED;
#endif
    socket_close(connection);
}

/* we have no networklayer. instead, attach the reusable buffer to the handle */
UA_Connection
UA_ClientConnectionTCP(UA_ConnectionConfig conf, const char *endpointUrl,
                       UA_Logger logger) {
#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 = socket_write;
    connection.recv = socket_recv;
    connection.close = ClientNetworkLayerClose;
    connection.free = NULL; /* Not used in the client */
    connection.getSendBuffer = ClientNetworkLayerGetBuffer;
    connection.releaseSendBuffer = ClientNetworkLayerReleaseBuffer;
    connection.releaseRecvBuffer = ClientNetworkLayerReleaseBuffer;

    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(logger, UA_LOGCATEGORY_NETWORK,
                       "Server url is invalid: %s", endpointUrl);
        return connection;
    }
    if(port == 0) {
        port = 4840;
        UA_LOG_INFO(logger, UA_LOGCATEGORY_NETWORK,
                    "No port defined, using standard port %d", port);
    }
    memcpy(hostname, hostnameString.data, hostnameString.length);
    hostname[hostnameString.length] = 0;

    struct addrinfo hints, *server;
    memset(&hints, 0, sizeof(hints));
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_family = AF_INET;
    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(logger, UA_LOGCATEGORY_NETWORK,
                       "DNS lookup of %s failed with error %s",
                       hostname, gai_strerror(error));
        return connection;
    }

    /* Get a socket */
    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(logger, UA_LOGCATEGORY_NETWORK,
                       "Could not create client socket");
        freeaddrinfo(server);
        return connection;
    }

    /* Connect to the server */
    connection.sockfd = (UA_Int32)clientsockfd; /* cast for win32 */
    error = connect(clientsockfd, server->ai_addr, WIN32_INT server->ai_addrlen);
    freeaddrinfo(server);
    if(error < 0) {
        ClientNetworkLayerClose(&connection);
#ifdef _WIN32
        wchar_t *s = NULL;
        FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                       FORMAT_MESSAGE_FROM_SYSTEM |
                       FORMAT_MESSAGE_IGNORE_INSERTS,
                       NULL, WSAGetLastError(),
                       MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                       (LPWSTR)&s, 0, NULL);
        UA_LOG_WARNING(logger, UA_LOGCATEGORY_NETWORK,
                       "Connection to %s failed. Error: %d: %S",
                       endpointUrl, WSAGetLastError(), s);
        LocalFree(s);
#else
        UA_LOG_WARNING(logger, UA_LOGCATEGORY_NETWORK,
                       "Connection to %s failed. Error: %d: %s",
                       endpointUrl, errno, strerror(errno));
#endif
        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(logger, UA_LOGCATEGORY_NETWORK,
                       "Couldn't set SO_NOSIGPIPE");
#endif

    return connection;
}