/**************************************************************************** * TCPserver.c * * J.Rogers, Jan/2003 * * * * Pedagogical TCP server example * * Usage: * * TCPserver [PORT] * * * * Listens at PORT (default 50000) * * Accepts connections * * Logs connection to stdout * * Echos any data received over connection except "q\r\n" which closes * * data connection and "x\r\n" which kills server * * Logs each message to stdout as it is received * ****************************************************************************/ #include // for printf() and perror() #include // for system dependent types #include // for socket stuff #include // for INET protocols and addresses #include // for inet_ntop() #include // for getprotobyname() #include // for errno #include // for strtol() #include // for close() #define TRUE ( 0 == 0 ) #define FALSE !TRUE const int DEFAULT_PORT = 50000; // Default server port const int MAX_QUEUE = 16; // Maximum number of pending connections const int BUFLEN = 1024; // Data buffer length const int NAMELEN = 16; // Max length of dotted octet string // Uniform error handler void errorExit( char* errmsg ); // Extract port from command line arguments int parsePort( int argc, char** argv); /**************************************************************************** * main * ****************************************************************************/ int main( int argc, char** argv ) { int port = parsePort( argc, argv ); // Server port number int ssock; // Server socket descriptor struct sockaddr_in saddr; // Server socket address (See ip(7)) int dsock; // Data socket descriptor struct sockaddr_in daddr; // Data socket address (See ip(7)) socklen_t daddr_length = sizeof( daddr ); char ddots[NAMELEN]; // const int OptionOn = TRUE; // setsockopt option int quit = FALSE; // Close connection flag ("q") int die = FALSE; // Exit flag ("x") char buffer[ BUFLEN ]; // I/O buffer int msglen; // length of received message // Create socket // getprotobyname() returns a protoent struct // the actual protocol number is in its p_proto field ssock = socket( PF_INET, // IPv4 internet protocols SOCK_STREAM, // connection oriented reliable transport getprotobyname("tcp")->p_proto); // Protocol number if ( ssock < 0 ) errorExit( "Could not create server socket" ); // set SO_REUSEADDR socket option // allows rebinding port without waiting for previous connection to time out if ( setsockopt( ssock, // Socket SOL_SOCKET, // Option is Socket level option SO_REUSEADDR, // Option name &OptionOn, sizeof( OptionOn ) ) // Option value < 0 ) errorExit( "Problems setting REUSEADDR" ); // Bind socket // Build socket address // sockaddr_in is the structure of internet domain socket addresses: // (See ip(7). Machine dependent types as given here are typical.) // struct sockaddr_in // { // short sin_family; --- should be AF_INET // u_short sin_port; --- Port number // struct in_addr sin_addr; --- Internet address. // unsigned char sin_zero[...] --- pad (unused) // }; // where in_addr is the structure of an internet domain address: // (See ip(7).) // struct in_addr // { // u_long s_addr; // }; saddr.sin_family = AF_INET; // IPv4 Address Family saddr.sin_addr.s_addr = htonl(INADDR_ANY); // bind to all local interfaces saddr.sin_port = htons( port ); // must be in network byte order // Bind socket address if ( bind( ssock, // Socket ( struct sockaddr * ) &saddr, // address sizeof( saddr ) ) < 0 ) errorExit( "Could not bind server port" ); // Begin listening at server port if ( listen( ssock, // Socket MAX_QUEUE) // Maximum number of pending connections < 0 ) errorExit( "Could not listen at server port" ); printf("Echoing at port %d\n", ntohs(saddr.sin_port) ); // Service connections // This is single-threaded, it services connections one at a time // although up to MAX_QUEUE connections may be pending while ( !die ) { // Accept new data socket // The third parameter is both input and output // When called it must point to var holding the addresss struct length // On exit var contains the actual length of the address returned dsock = accept( ssock, // Socket ( struct sockaddr * ) &daddr, // Gets client address &daddr_length ); // Length of address if ( dsock < 0 ) errorExit( "Failed to accept connection" ); // Log connection // inet_ntop() converts network addresses to dotted octet strings // Here we are only interested in the return value, which is a // pointer to the string, but we must provide the buffer in any case printf("Connection from %s:%d\n", inet_ntop( AF_INET, // Address Family &daddr.sin_addr, // address structure (in_addr) ddots, NAMELEN // buffer to hold string ), ntohs(daddr.sin_port) ); // Echo until "q\r\n" or "x\r\n" is recvd quit = FALSE; while ( !( quit || die ) ) { // Recieve data from socket // Last argument holds option flags---none here. msglen = recv( dsock, buffer, BUFLEN, 0 ); if ( msglen < 0 ) errorExit( " Failed to recv from data socket" ); // Log message // Add string terminator if ( msglen < BUFLEN ) buffer[msglen] = '\0'; else buffer[msglen-1] = '\0'; printf("Message from %s:%d::%s", inet_ntop( AF_INET, // Address Family &daddr.sin_addr, // address structure (in_addr) ddots, NAMELEN // buffer to hold string ), ntohs(daddr.sin_port), // convert network -> host order buffer); // if message is "x\r\n" set exit flag die = ( msglen == 3 && buffer[0] == 'x' ); // if message is "q\r\n" or "x\r\n" set close flag quit = ( msglen == 3 && buffer[0] == 'q' ) || die; if ( !quit ) { // we assume blocking send // if fewer than msglen chars are sent we take it as an error if ( send ( dsock, // socket buffer, msglen, // message, length MSG_NOSIGNAL ) // Flags: no SIG_PIPE on error < msglen ) errorExit( "Failed to send echo" ); } } // Close data socket printf("Closing %s:%d\n", ddots, ntohs(daddr.sin_port) ); close( dsock ); } printf("Shutting down\n"); close( ssock ); exit( EXIT_SUCCESS ); } /**************************************************************************** * void errorExit( char* errmsg ) * * Log errmsg and system explanation of most recent error to stderr * * Exit with EXIT_FAILURE * ****************************************************************************/ void errorExit( char* errmsg ) { perror( errmsg ); exit( EXIT_FAILURE ); } /**************************************************************************** * int parsePort( int argc, char** argv ) * * if no command line arguments returns DEFAULT_PORT * * if exactly one command line argument parses that as port number * * otherwise prints usage message and exits with failure * ****************************************************************************/ int parsePort( int argc, char** argv) { int portno = DEFAULT_PORT; // Port number if ( argc == 2 ) portno = strtol( argv[1], NULL, 10 ); if ( argc > 2 ) { printf("USAGE: %s [port]\n", argv[0]); exit( EXIT_FAILURE ); } return portno; }