UDP回显程序

udpserver.c

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <error.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <strings.h>

int main(int argc, char *argv[])
{
    struct sockaddr_in server;
    struct sockaddr_in source;
    socklen_t len;
    char recv[1024];
    int fd;
    int n;

    fd = socket(AF_INET,SOCK_DGRAM,0);
    if(fd < 0) {
        printf("socket error\n");
    }
    bzero(&source,sizeof(source));
    bzero(&server,sizeof(server));
    server.sin_family = AF_INET;
    server.sin_port = htons(20000);
    server.sin_addr.s_addr = htonl(INADDR_ANY);

    if(bind(fd,(struct sockaddr*)&server,sizeof(struct sockaddr)) < 0) {
        printf("bind error\n");
        close(fd);
    }
    len = sizeof(source);
    while(1) {

        n = recvfrom(fd,recv,1024,0,(struct sockaddr*)&source,&len);

        if(n > 0) {
            sendto(fd,recv,n,0,(struct sockaddr*)&source,len);
        }
    }
    return 0;
}

udpclient.c

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <string.h>

int main(int argc, char* argv[])
{
    int fd;
    int n;
    struct sockaddr_in server;
    char recv[1024];
    char send[1024];

    fd = socket(AF_INET,SOCK_DGRAM,0);


    if(fd < 0) {
        printf("socket error\n");
    }

    server.sin_family = AF_INET;
    server.sin_port = htons(20000);
    inet_pton(AF_INET,"10.155.3.243",&server.sin_addr);
    while(fgets(send,1024,stdin)!=NULL)
    {
        sendto(fd,send,strlen(send),0,(struct sockaddr*)&server,sizeof(struct sockaddr));
        n = recvfrom(fd,recv,1024,0,NULL,NULL);

        recv[n] = '\0';
        if(n >0)
            fputs(recv,stdout);
    }
    return 0;
}