udpechosvr.c

利用UDP client向server 发送信息

/* A sample program for echo server based on UDP. */

#include <stdio.h> /* for printf() and fprintf() */
#include <sys/socket.h> /* for socket() and bind() */
#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() */
#include <netinet/in.h> /*for htonl() and htons() */
//#define LOCAL_SERVER_PORT 7
#define ECHOMAX 255 /* Longest string to echo */
//void DieWithError(char *errorMessage); /* External error handling function */

int main(int argc, char *argv[])
{
	int sock; /* Socket */
	struct sockaddr_in echoServAddr; /* Local address */
	struct sockaddr_in echoClntAddr; /* Client address */
	unsigned int cliAddrLen; /* Length of incoming message */
	char echoBuffer[ECHOMAX]; /* Buffer for echo string */
	unsigned short echoServPort; /* Server port */
	int recvMsgSize,rc; /* Size of received message */
	
	if (argc != 2) 
	{
		fprintf(stderr,"Usage: %s <UDP SERVER PORT>\n", argv[0]);
		exit(1);
	}
	
	echoServPort = atoi(argv[1]); /* First arg: local port */
	printf("port number = %d\n",echoServPort);
	/* Create socket for sending/receiving datagrams */
	if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
		//DieWithError("socket() failed");
		printf("socket() failed.\n");
	/* Construct local address structure */
	memset(&echoServAddr, 0, sizeof(echoServAddr));
	echoServAddr.sin_family = AF_INET;
	echoServAddr.sin_addr.s_addr = htonl(INADDR_ANY);
	echoServAddr.sin_port =htons(echoServPort); 
	printf("address family = %d\n",echoServAddr.sin_family);
	printf("server address converted = %d\n",htonl(INADDR_ANY));
	printf("server port converted = %d\n",htons(echoServPort));
	printf("server address in number = %d\n",echoServAddr.sin_addr.s_addr);
	printf("server address = %s\n",inet_ntoa(echoServAddr.sin_addr));
	printf("server port = %d\n",echoServAddr.sin_port);
	/* Bind to the local address */
	//if (bind(sock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) < 0)
	rc = bind(sock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr));
	if (rc<0)
		//DieWithError("bind() failed");
		printf("bind() failed.\n");
	
	for (;;) /* Run forever */
	{
		/* Set the size of the in-out parameter */
		cliAddrLen = sizeof(echoClntAddr);
		/* Block until receive message from a client */
		if ((recvMsgSize = recvfrom(sock, echoBuffer, ECHOMAX, 0,
				(struct sockaddr *) &echoClntAddr, &cliAddrLen)) < 0)
			//DieWithError("recvfrom() failed");
			printf("recvfrom() failed.\n");
		printf("Handling client %s\n", inet_ntoa(echoClntAddr.sin_addr));
		/* Send received datagram back to the client */
		if (sendto(sock, echoBuffer, recvMsgSize, 0,
					(struct sockaddr *) &echoClntAddr, sizeof(echoClntAddr)) != recvMsgSize)
			//DieWithError("sendto() sent a different number of bytes than expected");
			printf("sendto() sent a different number of bytes than expected.\n");
	}
	/* NOT REACHED */
}