TCP Client

In this example, we demonstrate creation of a TCP client to connect to the server from the previous section. You can run it using zig build run-04-02 -- <port>.

const std = @import("std");
const net =;
const print = std.debug.print;

pub fn main() !void {
    var args = std.process.args();
    // The first (0 index) Argument is the path to the program.
    _ = args.skip();
    const port_value = orelse {
        print("expect port as command line argument\n", .{});
        return error.NoPort;
    const port = try std.fmt.parseInt(u16, port_value, 10);

    const peer = try net.Address.parseIp4("", port);
    // Connect to peer
    const stream = try net.tcpConnectToAddress(peer);
    defer stream.close();
    print("Connecting to {}\n", .{peer});

    // Sending data to peer
    const data = "hello zig";
    var writer = stream.writer();
    const size = try writer.write(data);
    print("Sending '{s}' to peer, total written: {d} bytes\n", .{ data, size });
    // Or just using `writer.writeAll`
    // try writer.writeAll("hello zig");

By default, the program connects with IPv4. If you want IPv6, use ::1 instead of, replace net.Address.parseIp4 by net.Address.parseIp6.

Last change: 2024-07-04, commit: e577a80