14、socket编程实现回声客户端

所谓“回声”，是指客户端向服务器发送一条数据，服务器再将数据原样返回给客户端，就像声音一样，遇到障碍物会被“反弹回来”。
对！客户端也可以使用 write() / send() 函数向服务器发送数据，服务器也可以使用 read() / recv() 函数接收数据。

服务端代码 server.c：

#include <stdio.h>
/* For socket functions*/
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
int main(int c, char ** v)
{
    /* 创建Socket */
    int serverSock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (serverSock < 0)
    {
        printf("socket error\n");
        return 1;
    }
    /* 绑定Socket */
    struct sockaddr_in addr = {0};
    addr.sin_family         = AF_INET;
    /* 绑定IP地址为0，即绑定所有网卡 */
    //addr.sin_addr.s_addr  = inet_addr("100.95.139.78");
    addr.sin_port   = htons(8093);
    if (0 != bind(serverSock, (struct sockaddr*)&addr, sizeof(addr)))
    {
        printf("bind error errno = %d.\n", errno);
        return 1;
    }
    /* 启动监听 */
    if (0 != listen(serverSock, 20))
    {
        printf("listen error\n");
        return 1;
    }
    /* 等待客户端连接 */
    struct sockaddr_in clientAddr;
    socklen_t addrLen = sizeof(clientAddr);
    int clientSock = accept(serverSock, (struct sockaddr *)&clientAddr, &addrLen);
    /* 接收数据 */
    char buf[512] = {0};
    int len = recv(clientSock, buf, 512, 0);
    /* 发送数据 */
    send(clientSock ,buf, len, 0);
    /* 使用read/write函数进行Socket套接字读写 */
    //int len = read(clientSock, buf, 512);
    //write(clientSock, buf, len);
    /* 关闭Socket */
    close(clientSock);
    close(serverSock);
    return 0;
}

客户端代码 client.c

#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
int main(int c, char ** v)
{
    /* 创建Socket */
    int sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (sock <= 0)
    {
        printf("socket error errno = %d.\n", errno);
    }
    /* 连接服务端 */
    struct sockaddr_in addr = {0};
    addr.sin_family         = AF_INET;
    addr.sin_port           = htons(8093);
    addr.sin_addr.s_addr    = inet_addr("127.0.0.1");
    connect(sock, (struct sockaddr*)&addr, sizeof(addr));
    char buf[] = "My Name is Weiyyi, I am 2 months old.";
    send(sock, buf, sizeof(buf), 0);
    char recvBuf[128] = {0};
    recv(sock, recvBuf, 128, 0);
    close(sock);
    return 0;
}