Socket編程實踐(13) --UDP編程基礎(1)

標籤：socket   linux   udp   cc++   伺服器   

UDP特點

    無串連,面向資料報(基於訊息,不會粘包)的Data Transmission Service;

    不可靠(可能會丟包),但一般情況下UDP更加高效;

UDP客戶/服務基本模型

UDP基礎API

1.Recvfrom

SYNOPSIS

       #include <sys/types.h>       #include <sys/socket.h>       ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags,                        struct sockaddr *src_addr, socklen_t *addrlen);

2.Sendto

SYNOPSIS

       #include <sys/types.h>       #include <sys/socket.h>       ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen);

實踐:一個簡陋的echo回聲server/client

//server.cpp#include "commen.h"int main(){    //建立UDP socket    int sockfd = socket(AF_INET,SOCK_DGRAM,0);    if (sockfd == -1)    {        err_exit("socket error");    }    //填寫server端資訊    struct sockaddr_in serverAddr;    serverAddr.sin_family = AF_INET;    serverAddr.sin_port = htons(9001);    serverAddr.sin_addr.s_addr =INADDR_ANY;    //綁定server端連接埠號碼    if (bind(sockfd,(struct sockaddr *)&serverAddr,sizeof(serverAddr)) == -1)    {        err_exit("bind error");    }    char buf[BUFSIZ];    struct sockaddr_in peerAddr;    socklen_t peerLen = sizeof(peerAddr);    while (true)    {        memset(buf,0,sizeof(buf));        int readCount = 0;        //接收從用戶端發送過來的資料        if ((readCount = recvfrom(sockfd,buf,sizeof(buf),0,(struct sockaddr *)&peerAddr,&peerLen)) == -1)        {            err_exit("recvfrom error");        }        //列印用戶端資訊        cout << "Client: " << endl;        cout << "\tsin_port: " << ntohs(peerAddr.sin_port) << endl;        cout << "\tsin_addr: " << inet_ntoa(peerAddr.sin_addr) << endl;        //將用戶端發送來的資訊回寫回去        if (sendto(sockfd,buf,sizeof(buf),0,(struct sockaddr *)&peerAddr,peerLen) == -1)        {            err_exit("sendto error");        }        buf[readCount] = 0;        //輸出到螢幕        fputs(buf,stdout);    }    return 0;}

//client.cpp#include "commen.h"int main(){    //建立UDP socket    int sockfd = socket(AF_INET,SOCK_DGRAM,0);    if (sockfd == -1)    {        err_exit("socket error");    }    //填寫server端資訊    struct sockaddr_in serverAddr;    serverAddr.sin_family = AF_INET;    serverAddr.sin_port = htons(9001);    serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");    char buf[BUFSIZ];    //從鍵盤接收資料    while (fgets(buf,sizeof(buf),stdin) != NULL)    {        //向server端傳送資料        if (sendto(sockfd,buf,strlen(buf),0,(struct sockaddr *)&serverAddr,sizeof(serverAddr)) == -1)        {            err_exit("sendto error");        }        memset(buf,0,sizeof(buf));        int readCount = 0;        //從server端接收資料,並且忽略server端資訊recvfrom(xx,xx,xx,xx,NULL,NULL)        if ((readCount = recvfrom(sockfd,buf,sizeof(buf),0,NULL,NULL)) == -1)        {            err_exit("recvfrom error");        }        buf[readCount] = 0;        //將資料寫到螢幕        fputs(buf,stdout);    }    return 0;}

實驗結果:

查看連接埠:

附-commen.h

#ifndef COMMEN_H_INCLUDED#define COMMEN_H_INCLUDED#include <unistd.h>#include <signal.h>#include <errno.h>#include <fcntl.h>#include <sys/types.h>#include <sys/wait.h>#include <sys/stat.h>#include <sys/ipc.h>#include <sys/shm.h>#include <sys/msg.h>#include <sys/sem.h>#include <sys/socket.h>#include <sys/select.h>#include <arpa/inet.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <string.h>#include <stdio.h>#include <stdlib.h>#include <iostream>using namespace std;void err_exit(std::string str){    perror(str.c_str());    exit(EXIT_FAILURE);}void peerClosePrint(std::string str = "peer connect closed"){    cerr << str << endl;    _exit(0);}#endif // COMMEN_H_INCLUDED

附-Makefile

CC = g++ CPPFLAGS = -Wall -g -pthreadBIN = server clientSOURCES = $(BIN.=.cpp).PHONY: clean all all: $(BIN)clean:    -rm -rf $(BIN) bin/ obj/ core

Socket編程實踐(13) --UDP編程基礎(1)