6 // Written by Curtis Olson, started November 1999.
8 // Copyright (C) 1999 Curtis L. Olson - curt@flightgear.org
10 // This program is free software; you can redistribute it and/or
11 // modify it under the terms of the GNU General Public License as
12 // published by the Free Software Foundation; either version 2 of the
13 // License, or (at your option) any later version.
15 // This program is distributed in the hope that it will be useful, but
16 // WITHOUT ANY WARRANTY; without even the implied warranty of
17 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 // General Public License for more details.
20 // You should have received a copy of the GNU General Public License
21 // along with this program; if not, write to the Free Software
22 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
27 #ifndef _SG_SOCKET_HXX
28 #define _SG_SOCKET_HXX
32 # error This library requires C++
35 #include <simgear/compiler.h>
39 #include <simgear/math/sg_types.hxx>
40 #include <simgear/io/iochannel.hxx>
48 #define SG_MAX_SOCKET_QUEUE 32
52 * A socket I/O class based on SGIOChannel.
54 class SGSocket : public SGIOChannel {
57 typedef SOCKET SocketType;
59 typedef int SocketType;
60 # define INVALID_SOCKET (-1)
67 char save_buf[ 2 * SG_IO_MAX_MSG_SIZE ];
72 short unsigned int port;
73 int sock_style; // SOCK_STREAM or SOCK_DGRAM
77 // make a server (master listening) socket
78 SocketType make_server_socket();
80 // make a client socket
81 SocketType make_client_socket();
84 size_t readsocket( int fd, void *buf, size_t count );
85 size_t writesocket( int fd, const void *buf, size_t count );
86 #if !defined(_MSC_VER)
87 int closesocket(int fd);
91 // Ensure winsock has been initialised.
92 static bool wsock_init;
93 static bool wsastartup();
99 * Create an instance of SGSocket.
101 * When calling the constructor you need to provide a host name, a
102 * port number, and a socket style. The convention used by the
103 * SGSocket class is that the server side listens and the client
104 * side sends. For a server socket, the host name should be
105 * empty. For a server, the port number is optional, if you do not
106 * specify a port, the system will assign one. For a client
107 * socket, you need to specify both a destination host and
108 * destination port. For both client and server sockets you must
109 * specify the socket type. Type must be either udp or tcp. Here's
110 * a quick breakdown of the major differences between UDP and TCP
113 * TCP sockets are the type where you establish a connection and
114 * then can read and write to the socket from both ends. If one
115 * end of TCP socket connect quits, the other end will likely
116 * segfault if it doesn't take special precautions. But, the nice
117 * thing about TCP connections is that the underlying protocol
118 * guarantees that your message will get through. This imposes a
119 * certain performance overhead though on the communication
120 * because the protocol must resend failed messages. TCP sockets
121 * are good for sending periodic command/response type messages
122 * where performance isn't a big issues, but reliability is.
124 * UDP sockets on the other hand are a lower level protocol and
125 * don't have the same sort of connection as TCP sockets. With UDP
126 * sockets, the server end just sits and listens for incoming
127 * packets from anywhere. The client end sends it's message and
128 * forgets about it. It doesn't care if there isn't even a server
129 * out there listening and all the packets are getting
130 * lost. Although systems/networks usually do a pretty good job
131 * (statistically) of getting your UDP packets to their
132 * destination, there is no guarantee that any particular packet
133 * will make it. But, because of this low level implementation and
134 * lack of error checking, UDP packets are much faster and
135 * efficient. UDP packets are good for sending positional
136 * information to synchronize two applications. In this case, you
137 * want the information to arrive as quickly as possible, and if
138 * you lose a packet, you'd rather get new updated information
139 * rather than have the system waste time resending a packet that
140 * is becoming older and older with every retry.
141 * @param host name of host if direction is SG_IO_OUT or SG_IO_BI
142 * @param port port number if we care to choose one.
143 * @param style specify "udp" or "tcp"
145 SGSocket( const string& host, const string& port, const string& style );
150 // If specified as a server (in direction for now) open the master
151 // listening socket. If specified as a client (out direction),
152 // open a connection to a server.
153 bool open( const SGProtocolDir d );
155 // read data from socket
156 int read( char *buf, int length );
158 // read data from socket
159 int readline( char *buf, int length );
161 // write data to a socket
162 int write( const char *buf, const int length );
164 // write null terminated string to a socket
165 int writestring( const char *str );
171 * Enable non-blocking mode.
172 * @return success/failure
176 /** @return the remote host name */
177 inline string get_hostname() const { return hostname; }
179 /** @return the port number (in string form) */
180 inline string get_port_str() const { return port_str; }
184 #endif // _SG_SOCKET_HXX