关于c:Linux网络开发必学教程2服务端编程初体验

客户端/服务端 编程模式

• 服务端长期保留于网络（公开本人的 IP 地址），并期待客户端连贯
• 客户端发动连贯动作，并期待服务端回应

• 特点：

  • 服务端无奈被动连贯客户端
  • 客户端只能依照预约义的形式（协定）连贯服务端

服务端编程模式

1. 筹备网络连接2. 绑定端口3. 进入端口监听状态4. 期待连贯

服务端外围工作：绑定 & 监听 & 接管

• 绑定：int bind(int sock, struct sockaddr *addr, socklen_t addrlen);
• 监听：int listen(int sock, int backlog);
• 接管：int accept(int sock, struct sockaddr *addr, socklen_t addrlen);

深度分析服务端

• 服务端 socket 只用于接管连贯，不进行理论通信
• 当接管到连贯时，accept() 函数返回与客户端通信的 socket
• 服务端 socket 产生用于通信的客户端 socket

所以，socket 到底是什么玩意？如何了解？

深刻了解 socket() 函数

• socket() 是什么？

  • socket() 是一个多功能函数

• socket() 返回的又是什么？

  • socket() 的返回值是用于通信的资源标识符

• socket() 还能做什么？

  • socket() 可提供不同类型的通信性能（本地过程间通信）

编程试验：服务端编程初体验

#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <stdio.h>#include <unistd.h>#include <string.h>int main(){    int server = 0;    struct sockaddr_in saddr = {0};    int clinet = 0;    struct sockaddr_in caddr = {0};    socklen_t asize = 0;    int len = 0;    char buf[32] = {0};    int r = 0;    server = socket(PF_INET, SOCK_STREAM, 0);    if (server == -1) {        printf("server socket error\n");        return -1;    }    saddr.sin_family = AF_INET;    saddr.sin_addr.s_addr = htonl(INADDR_ANY);    saddr.sin_port = htons(8899);    if (bind(server, (struct sockaddr*)&saddr, sizeof(saddr)) == -1) {        printf("server bind error\n");        return -1;    }    if (listen(server, 1) == -1) {        printf("server listen error\n");        return -1;    }    printf("server start success\n");    asize = sizeof(caddr);    clinet = accept(server, (struct sockaddr*)&caddr, &asize);    if (clinet == -1) {        printf("client accept error\n");        return -1;    }    printf("client: %d\n", clinet);    len = 0;    do {        int i = 0;                r = recv(clinet, buf, sizeof(buf), 0);        if (r > 0) {            len += r;        }        for (i=0; i<r; ++i) {            printf("%c", buf[i]);        }    } while (len < 64);    printf("\n");    send(clinet, "hello word!", 12, 0);    sleep(1);    close(clinet);    close(server);    return 0;}

INADDR_ANY => "0.0.0.0", 示意本机的连贯全副承受（如，本机有多个网卡进而有多个 IP 时）

客户端/服务端 编程的外围模式

• 服务端长时间运行（死循环）接管客户端的申请
• 客户端连贯后向服务端发送申请（协定数据）

服务端外围编程模式

编程试验：客户端/服务端编程试验

1. 服务端继续监听客户端连贯
2. 服务端被连贯后 echo 客户端数据
3. 服务端接管到 quit 后断开连接
4. 客户端接管用户输出并发送到服务端

服务端

#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <stdio.h>#include <unistd.h>#include <string.h>int main(){    int server = 0;    struct sockaddr_in saddr = {0};    int client = 0;    struct sockaddr_in caddr = {0};    socklen_t asize = 0;    int len = 0;    char buf[32] = {0};    int r = 0;    server = socket(PF_INET, SOCK_STREAM, 0);    if (server == -1) {        printf("server socket error\n");        return -1;    }    saddr.sin_family = AF_INET;    saddr.sin_addr.s_addr = htonl(INADDR_ANY);    saddr.sin_port = htons(8888);    if (bind(server, (struct sockaddr*)&saddr, sizeof(saddr)) == -1) {        printf("server bind error\n");        return -1;    }    if (listen(server, 1) == -1) {        printf("server listen error\n");        return -1;    }    printf("server start success\n");    while (1) {        asize = sizeof(caddr);        client = accept(server, (struct sockaddr*)&caddr, &asize);        if (client == -1) {            printf("client accept error\n");            return -1;        }        printf("client: %d\n", client);        do {            r = recv(client, buf, sizeof(buf), 0);            if (r > 0) {                printf("Receive: %s\n", buf);                if (strcmp(buf, "quit") != 0) {                    len = send(client, buf, r, 0);                }                else {                    break;                }            }         } while (r > 0);        close(client);    }    close(server);    return 0;}

客户端

#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <stdio.h>#include <unistd.h>#include <string.h>int main(){    int sock = 0;    struct sockaddr_in addr = {0};    int len = 0;    char buf[128] = {0};    char input[32] = {0};    int r = 0;    sock = socket(PF_INET, SOCK_STREAM, 0);    if (sock == -1) {        printf("socket error\n");        return -1;    }    addr.sin_family = AF_INET;    addr.sin_addr.s_addr = inet_addr("192.168.2.46");    addr.sin_port = htons(8888);    if (connect(sock, (struct sockaddr*)&addr, sizeof(addr)) == -1) {        printf("connect error\n");        return -1;    }    printf("connect success\n");    while (1) {        printf("Input: ");        scanf("%s", input);        len = send(sock, input, strlen(input) + 1, 0);        r = recv(sock, buf, sizeof(buf), 0);        if (r > 0) {            printf("Receive: %s\n", buf);        }        else {            break;        }    }    close(sock);    return 0;}

思考：如何加强服务端能力，同时反对多个客户端？