UDP(用户数据报协议)和套接字编程

来源：互联网发布：adobe dw cc 2017 mac 编辑：程序博客网时间：2024/05/16 08:05

这里写图片描述

源端口：发送方的端口号(需要对方回信是选用，不用时可全为0)
目的端口：终点交付报文时使用(把报文交给谁)
UDP长度：UDP用户数据报的长度，最小值8(仅有首部)
校验和：检测UDP用户数据报在传输中是否有错

UDP

特点

无连接的
尽最大努力交付，即不保证可靠交付
面向报文的
没有拥塞控制
支持一对一、一对多、多对多的交互通信
首部开销小，只有8个字节

UDP套接字(不需要监听和连接)

//server#include<stdio.h>#include<sys/types.h>#include<sys/socket.h>#include<string.h>#include<netinet/in.h>#include<arpa/inet.h>#include<stdlib.h>void usage(const char* proc){    printf("usage:%s [local_ip] [local_port]\n",proc);}int main(int argc,char*argv[]){    if(argc != 3)    {        usage(argv[0]);        return 1;    }    int sk = socket(AF_INET,SOCK_DGRAM,0);    if(sk < 0)    {        perror("socket");        return 2;    }    struct sockaddr_in local;    local.sin_family = PF_INET;    local.sin_port = htons(atoi(argv[2]));    local.sin_addr.s_addr =inet_addr(argv[1]);    if(bind(sk,(struct sockaddr*)&local,sizeof(local))<0)    {        perror("bind");        return 3;    }    while(1)    {        char buf[1024];        struct sockaddr_in client;        socklen_t len = sizeof(client);        ssize_t s = recvfrom(sk,buf,sizeof(buf)-1,0,(struct sockaddr*)&client,&len);        if(s > 0)        {            buf[s] = 0;            printf("client# %s\n",buf);            sendto(sk,buf,strlen(buf),0,(struct sockaddr*)&client,len);        }        else        {            close(sk);            printf("client quit...\n");            break;        }    }    return 0;}

//client#include<stdio.h>#include<sys/types.h>#include<sys/socket.h>#include<string.h>#include<netinet/in.h>#include<arpa/inet.h>#include<stdlib.h>void usage(const char* proc){    printf("usage:%s [local_ip] [local_port]\n",proc);}int main(int argc,char*argv[]){    if(argc != 3)    {        usage(argv[0]);        return 1;    }    int sk = socket(AF_INET,SOCK_DGRAM,0);    if(sk < 0)    {        perror("socket");        return 2;    }    char buf[1024];    struct sockaddr_in server;    server.sin_family = PF_INET;    server.sin_port = htons(atoi(argv[2]));    server.sin_addr.s_addr = inet_addr(argv[1]);    socklen_t len = sizeof(server);    while(1)    {        printf("Please Enter#:");        fflush(stdout);        ssize_t s = read(0,buf,sizeof(buf)-1);        if(s > 0)        {            buf[s-1] = 0;            sendto(sk,buf,sizeof(buf)-1,0,(struct sockaddr*)&server,len);            s = recvfrom(sk,buf,sizeof(buf)-1,0,(struct sockaddr*)&server,&len);            if(s>0)            {                buf[s] = 0;                printf("server echo#: %s\n",buf);            }        }    }}

//makefile.PHONY:allall:udp_server udp_clientudp_client:udp_client.c    gcc -o $@ $^udp_server:udp_server.c    gcc -o $@ $^ .PHONY:cleanclean:    rm -f udp_server udp_client

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