socket修改TCP发送缓冲区大小

#include <sys/socket.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>

#define BUFFER_SIZE 512

int main(int argc, char* argv[])
{
    if (argc <= 3)
    {
        printf("usage: %s ip_address port_number send_bufer_size\n", basename(argv[0]));
        return 1;
    }
    const char* ip = argv[1];
    int port = atoi(argv[2]);

    struct sockaddr_in server_address = {0};
    server_address.sin_family = AF_INET;
    inet_pton(AF_INET, ip, &server_address.sin_addr);
    server_address.sin_port = htons(port);

    int sock = socket(PF_INET, SOCK_STREAM, 0);
    assert(sock >= 0);

    int sendbuf = atoi(argv[3]);
    int len = sizeof(sendbuf);
    setsockopt(sock, SOL_SOCKET, SO_SNDBUF, &sendbuf, sizeof(sendbuf));
    getsockopt(sock, SOL_SOCKET, SO_SNDBUF, &sendbuf, (socklen_t*)&len);
    printf("the tcp send buffer size after setting is %d\n", sendbuf);

    if (connect(sock, (struct sockaddr*)&server_address, sizeof(server_address)) != -1)
    {
        char buffer[BUFFER_SIZE];
        memset(buffer, 'a', BUFFER_SIZE);
        send(sock, buffer, BUFFER_SIZE, 0);
    }

    close(sock);
    return 0;
}