Help with UDP Server/Client Program
I am trying to set this up so that when the client makes a connection with the server, the server will send the current time back to the client, and the client will display it. I'm having a few problems.
*NOTE* I have edited both programs a bit, but I am getting an error message when trying to compile UDPServer. It is as follows ---
UDPServer.c: In function âSIGIOHandlerâ:
UDPServer.c:97: warning: passing argument 2 of âsendtoâ makes pointer from integer without a cast
UDPServer.c:100: error: expected âwhileâ before â}â token
I really am at a loss with all of this. Any help will be greatly appreciated.
UDPServer.c
UDPClient.cCode:#include <stdio.h> /* for printf() and fprintf() */ #include <sys/socket.h> /* for socket(), bind, and connect() */ #include <arpa/inet.h> /* for sockaddr_in and inet_ntoa() */ #include <stdlib.h> /* for atoi() and exit() */ #include <string.h> /* for memset() */ #include <unistd.h> /* for close() and getpid() */ #include <fcntl.h> /* for fcntl() */ #include <sys/file.h> /* for O_NONBLOCK and FASYNC */ #include <signal.h> /* for signal() and SIGALRM */ #include <errno.h> /* for errno */ #include <time.h> /* for time */ #define ECHOMAX 255 /* Longest string to echo */ void DieWithError(char *errorMessage); /* Error handling function */ void UseIdleTime(); /* Function to use idle time */ void SIGIOHandler(int signalType); /* Function to handle SIGIO */ int sock; /* Socket -- GLOBAL for signal handler */ int main(int argc, char *argv[]) { struct sockaddr_in echoServAddr; /* Server address */ unsigned short echoServPort; /* Server port */ struct sigaction handler; /* Signal handling action definition */ /* Test for correct number of parameters */ if (argc != 2) { fprintf(stderr,"Usage: %s <SERVER PORT>\n", argv[0]); exit(1); } echoServPort = atoi(argv[1]); /* First arg: local port */ /* Create socket for sending/receiving datagrams */ if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) DieWithError("socket() failed"); /* Set up the server address structure */ memset(&echoServAddr, 0, sizeof(echoServAddr)); /* Zero out structure */ echoServAddr.sin_family = AF_INET; /* Internet family */ echoServAddr.sin_addr.s_addr = htonl(INADDR_ANY); /* Any incoming interface */ echoServAddr.sin_port = htons(echoServPort); /* Port */ /* Bind to the local address */ if (bind(sock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) < 0) DieWithError("bind() failed"); /* Set signal handler for SIGIO */ handler.sa_handler = SIGIOHandler; /* Create mask that mask all signals */ if (sigfillset(&handler.sa_mask) < 0) DieWithError("sigfillset() failed"); /* No flags */ handler.sa_flags = 0; if (sigaction(SIGIO, &handler, 0) < 0) DieWithError("sigaction() failed for SIGIO"); /* We must own the socket to receive the SIGIO message */ if (fcntl(sock, F_SETOWN, getpid()) < 0) DieWithError("Unable to set process owner to us"); /* Arrange for nonblocking I/O and SIGIO delivery */ if (fcntl(sock, F_SETFL, O_NONBLOCK | FASYNC) < 0) DieWithError("Unable to put client sock into non-blocking/async mode"); /* Go off and do real work; echoing happens in the background */ for (;;) UseIdleTime(); /* NOTREACHED */ } void UseIdleTime() { printf(".\n"); sleep(3); /* 3 seconds of activity */ } void SIGIOHandler(int signalType) { time_t currentTime; struct sockaddr_in echoClntAddr; /* Address of datagram source */ unsigned int clntLen; /* Address length */ do /* As long as there is input... */ { /* Set the size of the in-out parameter */ clntLen = sizeof(echoClntAddr); printf("Handling client %s\n", inet_ntoa(echoClntAddr.sin_addr)); if (sendto(sock, currentTime, sizeof(currentTime), 0, (struct sockaddr *) &echoClntAddr, sizeof(echoClntAddr)) != sizeof(currentTime)) DieWithError("sendto() failed"); } } while (sizeof(currentTime) >= 0); /* Nothing left to receive */ }
DieWithError.cCode:#include <stdio.h> /* for printf() and fprintf() */ #include <sys/socket.h> /* for socket(), connect(), sendto(), and recvfrom() */ #include <arpa/inet.h> /* for sockaddr_in and inet_addr() */ #include <stdlib.h> /* for atoi() and exit() */ #include <string.h> /* for memset() */ #include <unistd.h> /* for close() and alarm() */ #include <errno.h> /* for errno and EINTR */ #include <signal.h> /* for sigaction() */ #define BUFFERMAX 255 /* Longest string to receive */ #define TIMEOUT_SECS 2 /* Seconds between retransmits */ #define MAXTRIES 5 /* Tries before giving up */ int tries=0; /* Count of times sent - GLOBAL for signal-handler access */ void DieWithError(char *errorMessage); /* Error handling function */ void CatchAlarm(int ignored); /* Handler for SIGALRM */ int main(int argc, char *argv[]) { int sock; /* Socket descriptor */ struct sockaddr_in echoServAddr; /* Echo server address */ struct sockaddr_in fromAddr; /* Source address of echo */ unsigned short echoServPort; /* Echo server port */ unsigned int fromSize; /* In-out of address size for recvfrom() */ struct sigaction myAction; /* For setting signal handler */ char *servIP; /* IP address of server */ char timeBuffer[BUFFERMAX+1]; /* Buffer for echo string */ int timeStringLen; /* Length of string to echo */ int respStringLen; /* Size of received datagram */ if ((argc < 2) || (argc > 3)) /* Test for correct number of arguments */ { fprintf(stderr,"Usage: %s <Server IP> [<Echo Port>]\n", argv[0]); exit(1); } servIP = argv[1]; /* First arg: server IP address (dotted quad) */ if (argc == 3) echoServPort = atoi(argv[2]); /* Use given port, if any */ else echoServPort = 7; /* 7 is well-known port for echo service */ /* Create a best-effort datagram socket using UDP */ if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) DieWithError("socket() failed"); /* Set signal handler for alarm signal */ myAction.sa_handler = CatchAlarm; if (sigfillset(&myAction.sa_mask) < 0) /* block everything in handler */ DieWithError("sigfillset() failed"); myAction.sa_flags = 0; if (sigaction(SIGALRM, &myAction, 0) < 0) DieWithError("sigaction() failed for SIGALRM"); /* Construct the server address structure */ memset(&echoServAddr, 0, sizeof(echoServAddr)); /* Zero out structure */ echoServAddr.sin_family = AF_INET; echoServAddr.sin_addr.s_addr = inet_addr(servIP); /* Server IP address */ echoServAddr.sin_port = htons(echoServPort); /* Server port */ /* Get a response */ fromSize = sizeof(fromAddr); alarm(TIMEOUT_SECS); /* Set the timeout */ while ((respStringLen = recvfrom(sock, timeBuffer, BUFFERMAX, 0, (struct sockaddr *) &fromAddr, &fromSize)) < 0) if (errno == EINTR) /* Alarm went off */ { if (tries < MAXTRIES) /* incremented by signal handler */ { printf("timed out, %d more tries...\n", MAXTRIES-tries); alarm(TIMEOUT_SECS); } else DieWithError("No Response"); } else DieWithError("recvfrom() failed"); /* recvfrom() got something -- cancel the timeout */ alarm(0); /* null-terminate the received data */ timeBuffer[respStringLen] = '\0'; printf("Received: %s\n", timeBuffer); /* Print the received data */ close(sock); exit(0); } void CatchAlarm(int ignored) /* Handler for SIGALRM */ { tries += 1; }
Code:#include <stdio.h> #include <stdlib.h> void DieWithError(char *errorMessage) { perror(errorMessage); exit(1); }
Originally Posted by handsomedan
