flightgear/scripts/example/fgfsclient.cxx

// $Id$
// g++ -O2 -g -pedantic -Wall fgfsclient.cxx -o fgfsclient -lstdc++
// USAGE: ./fgfsclient [hostname [port]]
// Public Domain

#include <errno.h>
#include <iostream>
#include <netdb.h>
#include <netinet/in.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>


const char* HOST = "localhost";
const unsigned PORT = 5501;
const int BUFLEN = 256;


class FGFSSocket
{
public:
    FGFSSocket(const char* name, unsigned port);
    ~FGFSSocket();

    int write(const char* msg, ...);
    const char* read(void);
    inline void flush(void);
    void settimeout(unsigned t) { _timeout = t; }

private:
    int close(void);

    int _sock;
    bool _connected;
    unsigned _timeout;
    char _buffer[BUFLEN];
    bool _isShutdown = false;
};


FGFSSocket::FGFSSocket(const char* hostname = HOST, unsigned port = PORT) : _sock(-1),
                                                                            _connected(false),
                                                                            _timeout(1)
{
    _sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (_sock < 0)
        throw("FGFSSocket/socket");

    struct hostent* hostinfo;
    hostinfo = gethostbyname(hostname);
    if (!hostinfo) {
        close();
        throw("FGFSSocket/gethostbyname: unknown host");
    }

    struct sockaddr_in serv_addr;
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(port);
    serv_addr.sin_addr = *(struct in_addr*)hostinfo->h_addr;

    if (connect(_sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0) {
        close();
        throw("FGFSSocket/connect");
    }
    _connected = true;
    try {
        write("data");
    } catch (...) {
        close();
        throw;
    }
}


FGFSSocket::~FGFSSocket()
{
    _isShutdown = true;
    close();
}


int FGFSSocket::close(void)
{
    if (_connected)
        write("quit");
    if (_sock < 0)
        return 0;
    int ret = ::close(_sock);
    _sock = -1;
    return ret;
}


int FGFSSocket::write(const char* msg, ...)
{
    va_list va;
    ssize_t len;
    char buf[BUFLEN];
    fd_set fd;
    struct timeval tv;

    FD_ZERO(&fd);
    FD_SET(_sock, &fd);
    tv.tv_sec = _timeout;
    tv.tv_usec = 0;
    if (!select(FD_SETSIZE, 0, &fd, 0, &tv))
        if (_isShutdown) // don't throw during dtor
            std::cout << "FGFSSocket::write/select: timeout exceeded" << std::endl;
        else
            throw("FGFSSocket::write/select: timeout exceeded");

    va_start(va, msg);
    vsnprintf(buf, BUFLEN - 2, msg, va);
    va_end(va);
    std::cout << "SEND: " << buf << std::endl;
    strcat(buf, "\015\012");

    len = ::write(_sock, buf, strlen(buf));
    if (len < 0)
        if (_isShutdown) // don't throw during dtor
            std::cout << "FGFSSocket::write error" << std::endl;
        else
            throw("FGFSSocket::write");

    return len;
}


const char* FGFSSocket::read(void)
{
    char* p;
    fd_set fd;
    struct timeval tv;
    ssize_t len;

    FD_ZERO(&fd);
    FD_SET(_sock, &fd);
    tv.tv_sec = _timeout;
    tv.tv_usec = 0;
    if (!select(FD_SETSIZE, &fd, 0, 0, &tv)) {
        if (_timeout == 0)
            return 0;
        else
            throw("FGFSSocket::read/select: timeout exceeded");
    }

    len = ::read(_sock, _buffer, BUFLEN - 1);
    if (len < 0)
        throw("FGFSSocket::read/read");
    if (len == 0)
        return 0;

    for (p = &_buffer[len - 1]; p >= _buffer; p--)
        if (*p != '\015' && *p != '\012')
            break;
    *++p = '\0';
    return strlen(_buffer) ? _buffer : 0;
}


inline void FGFSSocket::flush(void)
{
    int i = _timeout;
    _timeout = 0;
    while (read())
        ;
    _timeout = i;
}


int main(const int argc, const char* argv[])
try {
    const char* hostname = argc > 1 ? argv[1] : "localhost";
    int port = argc > 2 ? atoi(argv[2]) : 5501;

    FGFSSocket f(hostname, port);
    f.flush();
    f.write("set /controls/engines/engine[%d]/throttle %lg", 0, 1.0);
    f.write("set /controls/engines/engine[%d]/throttle %lg", 1, 1.0);
    f.write("get /sim/aircraft");
    const char* p = f.read();
    if (p)
        std::cout << "RECV: " << p << std::endl;
    return EXIT_SUCCESS;

} catch (const char s[]) {
    std::cerr << "Error: " << s << ": " << strerror(errno) << std::endl;
    return EXIT_FAILURE;

} catch (...) {
    std::cerr << "Error: unknown exception" << std::endl;
    return EXIT_FAILURE;
}

// vim:cindent