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>
42 #include <plib/netSocket.h>
46 #define SG_MAX_SOCKET_QUEUE 32
50 * A socket I/O class based on SGIOChannel.
52 class SGSocket : public SGIOChannel {
58 char save_buf[ 2 * SG_IO_MAX_MSG_SIZE ];
70 // make a server (master listening) socket
71 bool make_server_socket();
73 // make a client socket
74 bool make_client_socket();
76 // Poll for new connections or data to read.
82 * Create an instance of SGSocket.
84 * When calling the constructor you need to provide a host name, a
85 * port number, and a socket style. The convention used by the
86 * SGSocket class is that the server side listens and the client
87 * side sends. For a server socket, the host name should be
88 * empty. For a server, the port number is optional, if you do not
89 * specify a port, the system will assign one. For a client
90 * socket, you need to specify both a destination host and
91 * destination port. For both client and server sockets you must
92 * specify the socket type. Type must be either udp or tcp. Here's
93 * a quick breakdown of the major differences between UDP and TCP
96 * TCP sockets are the type where you establish a connection and
97 * then can read and write to the socket from both ends. If one
98 * end of TCP socket connect quits, the other end will likely
99 * segfault if it doesn't take special precautions. But, the nice
100 * thing about TCP connections is that the underlying protocol
101 * guarantees that your message will get through. This imposes a
102 * certain performance overhead though on the communication
103 * because the protocol must resend failed messages. TCP sockets
104 * are good for sending periodic command/response type messages
105 * where performance isn't a big issues, but reliability is.
107 * UDP sockets on the other hand are a lower level protocol and
108 * don't have the same sort of connection as TCP sockets. With UDP
109 * sockets, the server end just sits and listens for incoming
110 * packets from anywhere. The client end sends it's message and
111 * forgets about it. It doesn't care if there isn't even a server
112 * out there listening and all the packets are getting
113 * lost. Although systems/networks usually do a pretty good job
114 * (statistically) of getting your UDP packets to their
115 * destination, there is no guarantee that any particular packet
116 * will make it. But, because of this low level implementation and
117 * lack of error checking, UDP packets are much faster and
118 * efficient. UDP packets are good for sending positional
119 * information to synchronize two applications. In this case, you
120 * want the information to arrive as quickly as possible, and if
121 * you lose a packet, you'd rather get new updated information
122 * rather than have the system waste time resending a packet that
123 * is becoming older and older with every retry.
124 * @param host name of host if direction is SG_IO_OUT or SG_IO_BI
125 * @param port port number if we care to choose one.
126 * @param style specify "udp" or "tcp"
128 SGSocket( const string& host, const string& port, const string& style );
133 // If specified as a server (in direction for now) open the master
134 // listening socket. If specified as a client (out direction),
135 // open a connection to a server.
136 bool open( const SGProtocolDir d );
138 // read data from socket
139 int read( char *buf, int length );
141 // read data from socket
142 int readline( char *buf, int length );
144 // write data to a socket
145 int write( const char *buf, const int length );
147 // write null terminated string to a socket
148 int writestring( const char *str );
154 * Enable non-blocking mode.
155 * @return success/failure
159 /** @return the remote host name */
160 inline string get_hostname() const { return hostname; }
162 /** @return the port number (in string form) */
163 inline string get_port_str() const { return port_str; }
167 #endif // _SG_SOCKET_HXX