UDPEchoServer

#include <stdio.h>

#include <sys/socket.h>

#include <arpa/inet.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#define ECHOMAX 255

void DieWithError(char *errorMessage);

int main(int argc, char *argv[])

{

int sock;

struct sockaddr_in echoServAddr;

struct sockaddr_in echoClntAddr;

unsigned int cliAddrLen;

char echoBuffer[ECHOMAX];

unsigned short echoServPort;

int recvMsgSize;

if (argc != 2)

{

fprintf(stderr,"Usage: %s <UDP SERVER PORT> \n", argv[0]);

exit(1);

}

echoServPort = atoi(argv[1]);

if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)

DieWithError("socket() failed");

memset(&echoServAddr, 0, sizeof(echoServAddr));

echoServAddr.sin_family = AF_INET;

echoServAddr.sin_addr.s_addr = htonl(INADDR_ANY);

echoServAddr.sin_port = htons(echoServPort);

if (bind(sock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) < 0)

DieWithError("bind() failed");

for (;;)

{

cliAddrLen = sizeof(echoClntAddr);

if ((recvMsgSize = recvfrom(sock, echoBuffer, ECHOMAX, 0,

(struct sockaddr *) &echoClntAddr, &cliAddrLen)) < 0)

DieWithError("recvfrom() failed");

printf("Handling client %s \n", inet_ntoa(echoClntAddr.sin_addr));

if (sendto(sock, echoBuffer, recvMsgSize, 0,

(struct sockaddr *) &echoClntAddr, sizeof(echoClntAddr)) != recvMsgSize)

DieWithError("sendto() sent a different number of bytes than expected");

}

}