Linux UDP通信例子

UDP C/S编程的步骤如下图所示

////server.c
#include <sys/types.h>
#include <sys/socket.h>
#include<pthread.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
    if (argc != )
    {
        printf("Usage: %s port\n", argv[]);
        exit();
    }
    printf("Welcome! This is a UDP server, I can only received message from client and reply with same message\n");

    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_port = htons(atoi(argv[]));
    addr.sin_addr.s_addr = htonl(INADDR_ANY);

    int sock;
    if ( (sock = socket(AF_INET, SOCK_DGRAM, )) < )
    {
        perror("socket");
        exit();
    }
    if (bind(sock, (struct sockaddr *)&addr, sizeof(addr)) < )
    {
        perror("bind");
        exit();
    }
    char buff[];
    struct sockaddr_in clientAddr;
    int n;
    int len = sizeof(clientAddr);
    while ()
    {
        n = recvfrom(sock, buff, , , (struct sockaddr*)&clientAddr, &len);
        if (n>)
        {
            buff[n] = ;
            printf("%s %u says: %s\n", inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port), buff);
            n = sendto(sock, buff, n, , (struct sockaddr *)&clientAddr, sizeof(clientAddr));
            if (n < )
            {
                perror("sendto");
                break;
            }
        }
        else
        {
            perror("recv");
            break;
        }
    }
    return ;
}

///client.c
#include <sys/types.h>
#include <sys/socket.h>
#include<pthread.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
    if (argc != )
    {
        printf("Usage: %s ip port", argv[]);
        exit();
    }
    printf("This is a UDP client\n");
    struct sockaddr_in addr;
    int sock;

    if ( (sock=socket(AF_INET, SOCK_DGRAM, )) <)
    {
        perror("socket");
        exit();
    }
    addr.sin_family = AF_INET;
    addr.sin_port = htons(atoi(argv[]));
    addr.sin_addr.s_addr = inet_addr(argv[]);
    if (addr.sin_addr.s_addr == INADDR_NONE)
    {
        printf("Incorrect ip address!");
        close(sock);
        exit();
    }

    char buff[];
    int len = sizeof(addr);
    while ()
    {
        gets(buff);
        int n;
        n = sendto(sock, buff, strlen(buff), , (struct sockaddr *)&addr, sizeof(addr));
        if (n < )
        {
            perror("sendto");
            close(sock);
            break;
        }
        n = recvfrom(sock, buff, , , (struct sockaddr *)&addr, &len);
        if (n>)
        {
            buff[n] = ;
            printf("received:");
            puts(buff);
        }
        else if (n==)
        {
            printf("server closed\n");
            close(sock);
            break;
        }
        else if (n == -)
        {
            perror("recvfrom");
            close(sock);
            break;
        }
    }

    return ;
}