兩個(gè)進(jìn)程使用socket通信庇茫，A端阻塞在recv/read，B端close socket后嗜侮，通常情況下港令，A端的recv/read會(huì)返回0。一個(gè)簡(jiǎn)單的方法锈颗，可以構(gòu)造出"Connection reset by peer"錯(cuò)誤，A端recv/read返回-1的場(chǎng)景咪惠。
server端代碼如下：

#include<sys/types.h>
#include<sys/socket.h>
#include<stdio.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<pthread.h>
#include<stdlib.h>
#include<string.h>

int main(void)
{
    int server_sockfd, client_sockfd;
    int server_len, client_len;
    struct sockaddr_in server_address;
    struct sockaddr_in client_address;

    server_sockfd = socket(AF_INET, SOCK_STREAM, 0);

    server_address.sin_family = AF_INET;
    //注意：inet_addr返回的已經(jīng)是按照網(wǎng)絡(luò)字節(jié)序存儲(chǔ)的網(wǎng)絡(luò)地址了击吱，所以不能再加htonl了
    server_address.sin_addr.s_addr = inet_addr("10.0.2.15");
    server_address.sin_port = htons(11021);
    server_len = sizeof(server_address);
    bind(server_sockfd, (struct sockaddr*)&server_address, server_len);

    listen(server_sockfd, 5);
    printf("server waiting\n");

    client_len = sizeof(client_address);
    client_sockfd = accept(server_sockfd, (struct sockaddr*)&client_address, &client_len);

    printf("client connected.\n");

    //server不發(fā)、client不收遥昧，recv返回0覆醇，不會(huì)出現(xiàn)"connect reset by peer"錯(cuò)誤
    send(client_sockfd, "hello world", strlen("hello world"), 0);

    char str[1024] = {0};
    int len = recv(client_sockfd, str, 1023, 0);
    //recv換成read朵纷，同樣的效果
    //int len = read(client_sockfd, str, 1023);
    printf("recv len = %d\n", len);
    if (len == -1)
    {
        perror("recv: ");
    }

    printf("server end!!!!\n");

    return 0;
}

client端代碼如下：

#include<sys/types.h>
#include<sys/socket.h>
#include<stdio.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<stdlib.h>
#include<pthread.h>
#include<string.h>

int main(void)
{
    int sockfd;
    int len;
    struct sockaddr_in address;
    int result;

    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    address.sin_family = AF_INET;
    //注意：inet_addr函數(shù)返回的已經(jīng)是按網(wǎng)絡(luò)字節(jié)序存儲(chǔ)的網(wǎng)絡(luò)地址了坡锡，所以不能再加htonl了
    address.sin_addr.s_addr = inet_addr("10.0.2.15");
    address.sin_port = htons(11021);
    len = sizeof(address);

    result = connect(sockfd, (struct sockaddr*)&address, len);
    if (-1 == result)
    {
        perror("oops: client");
        exit(1);
    }
    else
    {
        printf("connect success.\n");
    }

    {
        char buf[128] = {0};
        //client不收奠伪，或者只收一部分?jǐn)?shù)據(jù)黍判，不把server發(fā)送過來的數(shù)據(jù)收完据某，就會(huì)出現(xiàn)recv返回-1实辑，connect reset by peer錯(cuò)誤
        //recv(sockfd, buf, 4, 0);
    }
    sleep(5);
    printf("client close socket fd\n");
    close(sockfd);
    sleep(5);

    printf("client end!!!!\n");

    return 0;
}

先啟動(dòng)server端对省，再啟動(dòng)client端簸呈，運(yùn)行結(jié)果如下：

image.png

經(jīng)過測(cè)試發(fā)現(xiàn)诫龙，B端close socket的時(shí)候落午，如果此前A向B發(fā)送的數(shù)據(jù)谎懦，沒有被B完全接收走，A端的recv/read就會(huì)返回-1溃斋，錯(cuò)誤原因?yàn)?Connection reset by peer"界拦。例如下面的情況：

1. A發(fā)送了數(shù)據(jù)，但B完全沒有接收
2. A發(fā)送了10個(gè)字節(jié)梗劫，但B只接收了4個(gè)字節(jié)

題外話：

1. A端阻塞在recv/read的時(shí)候享甸，如果A端close socket（例如，在一個(gè)子線程中去調(diào)用close）梳侨，recv/read是不會(huì)從阻塞中返回的蛉威。