Socket编程实践(6) --TCP服务器常见问题(1)

ssize_t readnint fd, void *buf, size_t count); ssize_t writen(int fd, const void *buf, size_t count);

ssize_t readn(int fd,void *buf,size_t count) { size_t nLeft = count; ssize_t nRead = 0; char *ptr = static_cast<char *>(buf); while (nLeft > 0) { if ((nRead = read(fd,ptr,nLeft)) < 0) { //1点东西都没读 if (nLeft == count) { return ⑴; //error } else { break; //error, return amount read so far } } else if (nRead == 0) { break; //EOF } nLeft -= nRead; ptr += nRead; } return count - nLeft; } ssize_t writen(int fd, const void *buf, size_t count) { size_t nLeft = count; ssize_t nWritten; const char *ptr = static_cast<const char *>(buf); while (nLeft > 0) { if ((nWritten = write(fd,ptr,nLeft)) < 0) { //1点东西都没写 if (nLeft == count) { return ⑴; //error } else { break; //error, return amount write so far } } else if (nWritten == 0) { break; //EOF } nLeft -= nWritten; ptr += nWritten; } return count - nWritten; }

struct TransStruct { int m_length; //报头:保存数据m_text的真实数据长度 char m_text[BUFSIZ]; //报文:保存真正要发送的数据 };

//server端完全代码及解析 #include "commen.h" //echo 服务器writen,readn 版 int main() { int sockfd = socket(AF_INET,SOCK_STREAM,0); if (sockfd == ⑴) { err_exit("socket error"); } //添加地址复用 int optval = 1; if (setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&optval,sizeof(optval)) == ⑴) { err_exit("setsockopt SO_REUSEADDR error"); } //绑定 struct sockaddr_in serverAddr; serverAddr.sin_family = AF_INET; serverAddr.sin_port = htons(8002); serverAddr.sin_addr.s_addr = INADDR_ANY; //绑定本机的任意1个IP地址 if (bind(sockfd,(struct sockaddr *)&serverAddr,sizeof(serverAddr)) == ⑴) { err_exit("bind error"); } //启动监听套接字 if (listen(sockfd,SOMAXCONN) == ⑴) { err_exit("listen error"); } struct sockaddr_in peerAddr; socklen_t peerLen = sizeof(peerAddr); while (true) { //接受链接 int peerSockfd = accept(sockfd, (struct sockaddr *)&peerAddr,&peerLen); if (peerSockfd == ⑴) { err_exit("accept error"); } //打印客户信息 cout << "Client:" << endl; cout << " sin_port: " << ntohs(peerAddr.sin_port) << endl; cout << " sin_addr: " << inet_ntoa(peerAddr.sin_addr) << endl; cout << " socket: " << peerSockfd << endl; //每有1个客户端连接进来,就fork1个子进程, //相应的业务处理由子进程完成,父进程继续监听 pid_t pid = fork(); if (pid == ⑴) { close(sockfd); close(peerSockfd); err_exit("fork error"); } else if (pid == 0) //子进程,处理业务 { close(sockfd); //子进程关闭监听套接字,由于子进程不负责监听凭务 struct TransStruct recvBuf; ssize_t readCount = 0; while (true) { memset(&recvBuf,0,sizeof(recvBuf)); //首先,从客户端读取报头长度 if ((readCount = readn(peerSockfd,&(recvBuf.m_length),4)) == ⑴) { err_exit("readn error"); } else if (readCount == 0) //如果链接关闭 { peerClosePrint("client connect closed"); } //根据报文实际长度,读取数据 if ((readCount = readn(peerSockfd,&(recvBuf.m_text),recvBuf.m_length)) == ⑴) { err_exit("readn error"); } else if (readCount == 0) { peerClosePrint("client connect closed"); } //将整体报文回写回客户端 if (writen(peerSockfd,&recvBuf,recvBuf.m_length+4) == ⑴) { err_exit("writen error"); } recvBuf.m_text[recvBuf.m_length] = 0; //写至终端 fputs(recvBuf.m_text,stdout); } } else if (pid > 0) //父进程 { close(peerSockfd); } } close(sockfd); return 0; }

//client端完全代码实现及解析 #include "commen.h" int main() { int sockfd = socket(AF_INET,SOCK_STREAM,0); if (sockfd == ⑴) { err_exit("socket error"); } //填写好服务器地址及其端口号 struct sockaddr_in serverAddr; serverAddr.sin_family = AF_INET; serverAddr.sin_port = htons(8002); serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1"); if (connect(sockfd,(struct sockaddr *)&serverAddr,sizeof(serverAddr)) == ⑴) { err_exit("connect error"); } int readCount = 0; struct TransStruct sendBuf; struct TransStruct recvBuf; //从键盘输入数据 while (fgets(sendBuf.m_text,sizeof(sendBuf.m_text),stdin) != NULL) { //保存的是真实报文的长度 sendBuf.m_length = strlen(sendBuf.m_text); //向server发送数据....+4的缘由:需要添加报首的4个字节报头的长度 if (writen(sockfd,&sendBuf,sendBuf.m_length+4) == ⑴) { err_exit("write socket error"); } //首先,从server端接收将要发送的数据报的长度 if ((readCount = readn(sockfd,&(recvBuf.m_length),4)) == ⑴) { err_exit("read socket error"); } else if (readCount == 0) { peerClosePrint("client connect closed"); } //然后,根据从server端读来的报文长度,读取报文 if ((readCount = readn(sockfd,&(recvBuf.m_text),recvBuf.m_length)) == ⑴) { err_exit("read socket error"); } else if (readCount == 0) { peerClosePrint("client connect closed"); } recvBuf.m_text[recvBuf.m_length] = 0; //将其回写到终端 fputs(recvBuf.m_text,stdout); memset(&sendBuf,0,sizeof(sendBuf)); memset(&recvBuf,0,sizeof(recvBuf)); } close(sockfd); return 0; }

#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 <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; //报文结构 struct TransStruct { int m_length; //报头:保存数据m_text的真实数据长度 char m_text[BUFSIZ]; //报文:保存真正要发送的数据 }; //出错退出 void err_exit(std::string str) { perror(str.c_str()); exit(EXIT_FAILURE); } //对端关闭链接退出 void peerClosePrint(std::string str = "peer connect closed") { cout << str << endl; _exit(0); } //信号捕获函数:上1篇博客中的代码需要使用的 void onSignal(int signalNumber) { switch (signalNumber) { case SIGUSR1: cout << "child receive SIGUSR1" << signalNumber << endl; _exit(0); case SIGUSR2: cout << "parent receive SIGUSR2: " << signalNumber << endl; _exit(0); default: cout << "RECV OTHRER SIGNAL" << endl; } } //经典的readn函数(来源:APUE) ssize_t readn(int fd,void *buf,size_t count) { size_t nLeft = count; ssize_t nRead = 0; char *ptr = static_cast<char *>(buf); while (nLeft > 0) { if ((nRead = read(fd,ptr,nLeft)) < 0) { //1点东西都没读 if (nLeft == count) { return ⑴; //error } else { break; //error, return amount read so far } } else if (nRead == 0) { break; //EOF } nLeft -= nRead; ptr += nRead; } return count - nLeft; } //经典的writen函数(来源:APUE) ssize_t writen(int fd, const void *buf, size_t count) { size_t nLeft = count; ssize_t nWritten; const char *ptr = static_cast<const char *>(buf); while (nLeft > 0) { if ((nWritten = write(fd,ptr,nLeft)) < 0) { //1点东西都没写 if (nLeft == count) { return ⑴; //error } else { break; //error, return amount write so far } } else if (nWritten == 0) { break; //EOF } nLeft -= nWritten; ptr += nWritten; } return count - nWritten; } #endif // COMMEN_H_INCLUDED