libuv 异步网络编程之 TCP helloworld

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发布于: 2020 年 08 月 10 日
指引学习 libuv 官网文档 http://docs.libuv.org/en/v1.x/guide/networking.html 网络编程部分。
Libuv 的网络编程跟 BSD socket 接口没什么区别，保持了同样概念的情况下，所有的操作都是异步的。相比 BSD 比较原始的操作，libuv 提供了 DNS 查询、封装 socket 参数等实用函数。
libuv 版本：1.38.1
TCP 服务端服务端程序的常规操作：
初始化地址
bind 该地址
开始 listen
accept 新连接
不过此处 accept 新连接是在回调函数 on_new_connection里。
之后才能对新连接 client进行读取数据/写入数据等操作。
TCP 客户端客户端程序连接服务端的常规操作：
初始化地址
连接服务端
连接服务端成功后，需要在回调函数 on_connected里去发送数据。
结果示例：
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完整代码https://github.com/Asphaltt/libuv-examples/tree/master/tcp-helloworld
server.c例子里没有接收客户端的数据，接收数据的操作参考客户端
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <uv.h>
static uv_loop_t *loop;
static void on_close(uv_handle_t* handle) {
    free(handle);
}
static void on_response_callback(uv_write_t* req, int status) {
    if (status < 0) {
        fprintf(stderr, "failed to response world to client, err: %s\n", uv_strerror(status));
    } else {
        printf("succeeded in responsing world to client\n");
        return;
    }
    fprintf(stderr, "uv_write error: %s\n", uv_strerror(status));
    if (status == UV_ECANCELED)
        return;
    assert(status == UV_EPIPE);
    uv_close((uv_handle_t*)req->handle, on_close);
    free(req);
}
void on_new_connection(uv_stream_t *conn, int status) {
    int r;
    uv_write_t wr;
    if (status < 0) {
        fprintf(stderr, "failed to create new connection, err: %s\n", uv_strerror(status));
        return;
    }
    uv_tcp_t *client = malloc(sizeof(uv_tcp_t));
    uv_tcp_init(loop, client);
    if ((r = uv_accept(conn, (uv_stream_t *)client)) != 0) {
        printf("failed to accept a new connection, err: %s\n", uv_strerror(r));
        return;
    }
    uv_buf_t b[] = {
        {.base = "world", .len = 5}
    };
    if ((r = uv_write(&wr, (uv_stream_t *)client, b, 1, on_response_callback)) != 0) {
        printf("failed to response world to client, err: %s\n", uv_strerror(r));
    }
}
int main() {
    struct sockaddr_in addr;
    uv_tcp_t server;
    int res = 0;
    loop = uv_default_loop();
    uv_tcp_init(loop, &server);
    if ((res = uv_ip4_addr("127.0.0.1", 10086, &addr)) != 0) {
        printf("failed to init listening address, err: %s\n", uv_strerror(res));
        return 1;
    }
    if ((res = uv_tcp_bind(&server, (const struct sockaddr *)&addr, 0)) != 0) {
        printf("failed to bind the listening address, err: %s\n", uv_strerror(res));
        return 2;
    }
    if ((res = uv_listen((uv_stream_t *)&server, 5, on_new_connection)) != 0) {
        printf("failed to listen on the address, err: %s\n", uv_strerror(res));
        return 3;
    }
    return uv_run(loop, UV_RUN_DEFAULT);
}
client.c
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <uv.h>
static uv_loop_t *loop;
static void on_close(uv_handle_t* handle) {
    free(handle);
}
static void on_shutdown(uv_shutdown_t *sd, int status) {
    if (status < 0) {
        fprintf(stderr, "failed to shutdown connection, err: %s\n", uv_strerror(status));
        return;
    } else {
        uv_close((uv_handle_t *)sd->handle, on_close);
    }
    free(sd);
}
void read_alloc_callback(uv_handle_t *handle, size_t suggested_size, uv_buf_t *buf) {
    buf->base = malloc(suggested_size);
    buf->len = suggested_size;
}
void read_callback(uv_stream_t *stream, ssize_t nread, const uv_buf_t *buf) {
    if (nread < 0) {
        fprintf(stderr, "failed to read from server, err: %s\n", uv_strerror(nread));
        free(buf->base);
        exit(1);
        return;
    } else if (nread > 0) {
        buf->base[nread] = '\0';
        printf("recv %s\n", buf->base);
        uv_shutdown_t *sd = malloc(sizeof(uv_shutdown_t));
        uv_shutdown(sd, stream, on_shutdown);
    }
    free(buf->base);
}
static void on_response_callback(uv_write_t* req, int status) {
    if (status < 0) {
        fprintf(stderr, "failed to write hello to server, err: %s\n", uv_strerror(status));
    } else {
        return;
    }
    fprintf(stderr, "uv_write error: %s\n", uv_strerror(status));
    if (status == UV_ECANCELED)
        return;
    assert(status == UV_EPIPE);
    uv_close((uv_handle_t *)req->handle, on_close);
    free(req);
}
void on_connected(uv_connect_t *conn, int status) {
    int r;
    uv_write_t wr;
    if (status < 0) {
        fprintf(stderr, "failed to dial to server, err: %s\n", uv_strerror(status));
        return;
    }
    uv_buf_t b[] = {
        {.base = "hello", .len = 5}
    };
    if ((r = uv_write(&wr, conn->handle, b, 1, on_response_callback)) != 0) {
        printf("failed to send hello to server, err: %s\n", uv_strerror(r));
        return;
    }
    printf("sent hello\n");
    if ((r = uv_read_start(conn->handle, read_alloc_callback, read_callback)) != 0) {
        printf("failed to start reading data from server, err: %s\n", uv_strerror(r));
        return ;
    }
}
int main() {
    int r;
    struct sockaddr_in addr;
    uv_tcp_t *client = malloc(sizeof(uv_tcp_t));
    uv_connect_t *connect = malloc(sizeof(uv_connect_t));
    loop = uv_default_loop();
    uv_tcp_init(loop, client);
    if ((r = uv_ip4_addr("127.0.0.1", 10086, &addr)) != 0) {
        printf("failed to init server address, err: %s\n", uv_strerror(r));
        return 1;
    }
    if ((r = uv_tcp_connect(connect, client, (const struct sockaddr *)&addr, on_connected)) != 0) {
        printf("failed to connect to server, err: %s\n", uv_strerror(r));
        return 2;
    }
    return uv_run(loop, UV_RUN_DEFAULT);
}
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