一、基于TCP的c/s交互流程
C/S
C/S
服务器端：
socket() → bind() → listen() → accept() → recv()/read() ↔ send()/write() → close()
创建socket → 绑定socket和端口号 → 监听端口号 → 接收来自客户端的连接请求 → 从socket中读取字符 → 关闭socket客户端：
socket() → connect() → send()/write() ↔ recv()/read() → close()
创建socket → 连接指定服务器的IP/端口号 → 向socket中写入信息 → 关闭socket
二、C++代码实现
1、server.cpp
按照该实现，服务器每次只能服务一个客户端。
#include <iostream>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include "cs.h"
#include "ErrCode.h"
using namespace std;
#define PORT 9977
#define MSG_SIZE 4096
#define MAX_LINE 20
int server() {
char cMsg[MSG_SIZE], sMsg[MSG_SIZE];
struct sockaddr_in serverAddr; // 一个将来与套接字绑定的结构体
memset(&serverAddr, 0, sizeof(serverAddr));
serverAddr.sin_port = (PORT); // 从服务器的PORT端口接收客户端信息
serverAddr.sin_family = AF_INET; // 协议簇，AF_INET表示TCP/IP协议
serverAddr.sin_addr.s_addr = htonl(INADDR_ANY); // 指定接收的信息来自于某个IP，这里随意
int fd_skt = socket(AF_INET, SOCK_STREAM, 0); // （1）socket函数新建套接字fd_skt
if (fd_skt < 0) {
perror("server socket err");
return SERVER_SOCKET_ERR;
}
if (bind(fd_skt, (struct sockaddr*)&serverAddr, sizeof(serverAddr)) < 0 ) { // （2）bind绑定套接字与serverAddr
perror("server bind err");
return SERVER_BIND_ERR;
}
if (listen(fd_skt, MAX_LINE) < 0) { // （3）listen监听套接字fd_skt
perror("server listen err");
return SERVER_LISTEN_ERR;
}
cout << "Listening..." << endl;
while(1) {
memset(cMsg, 0, sizeof(cMsg));
memset(sMsg, 0, sizeof(sMsg));
struct sockaddr_in clientAddr;
socklen_t length = sizeof(clientAddr);
int fd_client = accept(fd_skt, (struct sockaddr*)&clientAddr, &length);
// （4）accept接收连接请求：程序在此阻塞直至产生第一次握手
// 接收到的信息存于第二第三个参数中
// 返回值是新的文件描述符，用于后续read和write调用
if (fd_client < 0) {
perror("server accept err");
return SERVER_ACCEPT_ERR;
}
cout << "server: got connection from " << clientAddr.sin_addr.s_addr
<< ", port " << PORT
<< ", socket" << fd_client << endl;
while(1) {
int cLen = recv(fd_client, cMsg, sizeof(cMsg), 0); // （5）read将接收到的客户端消息存在cMsg中
if (cLen <= 0) {
perror("server recv err");
return SERVER_RECV_ERR;
}
cMsg[cLen] = '\0';
cout << "Receive message form <" << clientAddr.sin_addr.s_addr << ">: " << cMsg << endl;
cin.ignore(1024,'\n'); // 去除上一个cin残留在缓冲区的\n
cin.getline(sMsg, sizeof(sMsg)); // 不用cin，因为不能含空格
if(strcmp(sMsg, "quit\n") == 0){
break; // 结束对当前客户端的服务
}
if(send(fd_client, sMsg, strlen(sMsg), 0) <= 0) { // （6）send将服务器的消息发给客户端
perror("server send err");
return SERVER_SEND_ERR;
}
// recv和send的返回值：
// >0表示成功，返回实际发送或接受的字节数
// =0表示超时，对方主动关闭了连接过程
// <0出错
cout << "Send message to <" << clientAddr.sin_addr.s_addr << ">: " << sMsg << endl;
}
close(fd_client);
cout << "当前客户端已结束通信，是否继续等待其他客户端？（1 - 是， 0 - 否）" << endl;
bool isContinue = false;
cin >> isContinue;
if (!isContinue) {
break;
}
}
close(fd_skt);
return SUCCESS;
}
2、client.cpp
#include <iostream>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include "cs.h"
#include "ErrCode.h"
using namespace std;
#define PORT 9977
#define MAX_LINE 20
#define MSG_SIZE 4096
#define DEFAULT_SERVER "127.0.0.1"
int client() {
char cMsg[MSG_SIZE], sMsg[MSG_SIZE];
struct sockaddr_in serverAddr; // 一个将来与套接字绑定的结构体
memset(&serverAddr, 0, sizeof(serverAddr));
serverAddr.sin_port = (PORT); // 从客户端的PORT端口接收服务器信息
serverAddr.sin_family = AF_INET; // 协议簇，AF_INET表示TCP/IP协议
cout << "Please input the server address: (输入1连接默认服务器)" << endl;
char sAddr[20];
cin >> sAddr;
if (strcmp(sAddr, "1") == 0) {
if(inet_pton(AF_INET, DEFAULT_SERVER, (void *)&serverAddr.sin_addr) <= 0) {
perror("client inet_pton err");
return CLIENT_INETPTON_ERR;
}
}
else {
if(inet_pton(AF_INET, DEFAULT_SERVER, (void *)&serverAddr.sin_addr) <= 0) {
perror("client inet_pton err");
return CLIENT_INETPTON_ERR;
}
}
int fd_skt = socket(AF_INET, SOCK_STREAM, 0); // （1）socket函数新建套接字fd_skt
if (fd_skt < 0) {
perror("client socket err");
return CLIENT_SOCKET_ERR;
}
if (connect(fd_skt, (struct sockaddr*)&serverAddr, sizeof(serverAddr)) < 0) { //（2）connect向服务器发起连接请求
perror("client connect err");
return CLIENT_CONNECT_ERR;
}
cout << "Connect Success! \nBegin to chat..." << endl;
while(1) {
memset(cMsg, 0, sizeof(cMsg));
memset(sMsg, 0, sizeof(sMsg));
cin.ignore(1024,'\n'); // 去除上一个cin残留在缓冲区的\n
cin.getline(cMsg, sizeof(cMsg)); // 不用cin，因为不能含空格
if(strcmp(cMsg, "quit\n") == 0){
break;
}
if(send(fd_skt, cMsg, strlen(cMsg), 0) < 0) { // （3）send，客户端向服务端发消息
perror("client send err");
return CLIENT_SEND_ERR;
}
cout << "Send message to <" << serverAddr.sin_addr.s_addr << ">: " << cMsg << endl;
int sLen = recv(fd_skt, sMsg, sizeof(sMsg),0); // （4） recv，接收服务器发来的消息
if(sLen <= 0) {
perror("client recv err");
return CLIENT_RECV_ERR;
}
sMsg[sLen] = '\0';
cout << "Receive message form <" << serverAddr.sin_addr.s_addr << ">: " << sMsg << endl;
}
close(fd_skt);
}
3、main.cpp
#include <iostream>
#include "cs.h"
using namespace std;
int main() {
cout << "————————【chat start】————————" << endl;
while(1) {
cout << "Client or Server?" << endl;
char cs;
cin >> cs;
if (cs == 's') {
if(server() != 0){
break;
}
}
else if (cs == 'c') {
if(client() != 0){
break;
}
}
else {
cout << "err input" << endl;
}
}
cout << "————————【chat end】————————" << endl;
return 0;
}
4、ErrCode.h
#define SUCCESS 0
#define SERVER_SOCKET_ERR 1000
#define SERVER_BIND_ERR 1001
#define SERVER_LISTEN_ERR 1002
#define SERVER_ACCEPT_ERR 1003
#define SERVER_RECV_ERR 1004
#define SERVER_SEND_ERR 1005
#define CLIENT_INETPTON_ERR 1010
#define CLIENT_SOCKET_ERR 1011
#define CLIENT_CONNECT_ERR 1012
#define CLIENT_SEND_ERR 1013
#define CLIENT_RECV_ERR 1014
5、cs.h
#include <iostream>
int server();
int client();
3、运行效果
client
server
